Merge branch 'block-dir' of git://brick.kernel.dk/data/git/linux-2.6-block

12 files changed, 11454 insertions, 0 deletions

diff --git a/block/Kconfig b/block/Kconfig
new file mode 100644
index 00000000000..eb48edb80c1
--- /dev/null
+++ b/block/Kconfig
@@ -0,0 +1,14 @@
+#
+# Block layer core configuration
+#
+#XXX - it makes sense to enable this only for 32-bit subarch's, not for x86_64
+#for instance.
+config LBD
+	bool "Support for Large Block Devices"
+	depends on X86 || (MIPS && 32BIT) || PPC32 || ARCH_S390_31 || SUPERH || UML
+	help
+	  Say Y here if you want to attach large (bigger than 2TB) discs to
+	  your machine, or if you want to have a raid or loopback device
+	  bigger than 2TB.  Otherwise say N.
+
+source block/Kconfig.iosched
diff --git a/block/Kconfig.iosched b/block/Kconfig.iosched
new file mode 100644
index 00000000000..f3b7753aac9
--- /dev/null
+++ b/block/Kconfig.iosched
@@ -0,0 +1,69 @@
+
+menu "IO Schedulers"
+
+config IOSCHED_NOOP
+	bool
+	default y
+	---help---
+	  The no-op I/O scheduler is a minimal scheduler that does basic merging
+	  and sorting. Its main uses include non-disk based block devices like
+	  memory devices, and specialised software or hardware environments
+	  that do their own scheduling and require only minimal assistance from
+	  the kernel.
+
+config IOSCHED_AS
+	tristate "Anticipatory I/O scheduler"
+	default y
+	---help---
+	  The anticipatory I/O scheduler is the default disk scheduler. It is
+	  generally a good choice for most environments, but is quite large and
+	  complex when compared to the deadline I/O scheduler, it can also be
+	  slower in some cases especially some database loads.
+
+config IOSCHED_DEADLINE
+	tristate "Deadline I/O scheduler"
+	default y
+	---help---
+	  The deadline I/O scheduler is simple and compact, and is often as
+	  good as the anticipatory I/O scheduler, and in some database
+	  workloads, better. In the case of a single process performing I/O to
+	  a disk at any one time, its behaviour is almost identical to the
+	  anticipatory I/O scheduler and so is a good choice.
+
+config IOSCHED_CFQ
+	tristate "CFQ I/O scheduler"
+	default y
+	---help---
+	  The CFQ I/O scheduler tries to distribute bandwidth equally
+	  among all processes in the system. It should provide a fair
+	  working environment, suitable for desktop systems.
+
+choice
+	prompt "Default I/O scheduler"
+	default DEFAULT_AS
+	help
+	  Select the I/O scheduler which will be used by default for all
+	  block devices.
+
+	config DEFAULT_AS
+		bool "Anticipatory" if IOSCHED_AS=y
+
+	config DEFAULT_DEADLINE
+		bool "Deadline" if IOSCHED_DEADLINE=y
+
+	config DEFAULT_CFQ
+		bool "CFQ" if IOSCHED_CFQ=y
+
+	config DEFAULT_NOOP
+		bool "No-op"
+
+endchoice
+
+config DEFAULT_IOSCHED
+	string
+	default "anticipatory" if DEFAULT_AS
+	default "deadline" if DEFAULT_DEADLINE
+	default "cfq" if DEFAULT_CFQ
+	default "noop" if DEFAULT_NOOP
+
+endmenu
diff --git a/block/Makefile b/block/Makefile
new file mode 100644
index 00000000000..7e4f93e2b44
--- /dev/null
+++ b/block/Makefile
@@ -0,0 +1,10 @@
+#
+# Makefile for the kernel block layer
+#
+
+obj-y	:= elevator.o ll_rw_blk.o ioctl.o genhd.o scsi_ioctl.o
+
+obj-$(CONFIG_IOSCHED_NOOP)	+= noop-iosched.o
+obj-$(CONFIG_IOSCHED_AS)	+= as-iosched.o
+obj-$(CONFIG_IOSCHED_DEADLINE)	+= deadline-iosched.o
+obj-$(CONFIG_IOSCHED_CFQ)	+= cfq-iosched.o
diff --git a/block/as-iosched.c b/block/as-iosched.c
new file mode 100644
index 00000000000..a78e160b59a
--- /dev/null
+++ b/block/as-iosched.c
@@ -0,0 +1,2005 @@
+/*
+ *  linux/drivers/block/as-iosched.c
+ *
+ *  Anticipatory & deadline i/o scheduler.
+ *
+ *  Copyright (C) 2002 Jens Axboe <axboe@suse.de>
+ *                     Nick Piggin <nickpiggin@yahoo.com.au>
+ *
+ */
+#include <linux/kernel.h>
+#include <linux/fs.h>
+#include <linux/blkdev.h>
+#include <linux/elevator.h>
+#include <linux/bio.h>
+#include <linux/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 exited */
+	AS_TASK_IOSTARTED,	/* Process has started some IO */
+	AS_TASK_IORUNNING,	/* Process has completed some IO */
+};
+
+enum anticipation_status {
+	ANTIC_OFF=0,		/* Not anticipating (normal operation)	*/
+	ANTIC_WAIT_REQ,		/* The last read has not yet completed  */
+	ANTIC_WAIT_NEXT,	/* Currently anticipating a request vs
+				   last read (which has completed) */
+	ANTIC_FINISHED,		/* Anticipating but have found a candidate
+				 * or timed out */
+};
+
+struct as_data {
+	/*
+	 * run time data
+	 */
+
+	struct request_queue *q;	/* the "owner" queue */
+
+	/*
+	 * requests (as_rq s) are present on both sort_list and fifo_list
+	 */
+	struct rb_root sort_list[2];
+	struct list_head fifo_list[2];
+
+	struct 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 exit_no_coop;	/* probablility an exited task will
+					   not be part of a later cooperating
+					   request */
+	unsigned long new_ttime_total; 	/* mean thinktime on new proc */
+	unsigned long new_ttime_mean;
+	u64 new_seek_total;		/* mean seek on new proc */
+	sector_t new_seek_mean;
+
+	unsigned long current_batch_expires;
+	unsigned long last_check_fifo[2];
+	int changed_batch;		/* 1: waiting for old batch to end */
+	int new_batch;			/* 1: waiting on first read complete */
+	int batch_data_dir;		/* current batch 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 exited or timed out*/
+			ad->exit_prob = (7*ad->exit_prob + 256)/8;
+		}
+		if (!test_bit(AS_TASK_RUNNING, &aic->state)) {
+			/* process not "saved" by a cooperating request */
+			ad->exit_no_coop = (7*ad->exit_no_coop + 256)/8;
+		}
+	}
+	spin_unlock_irqrestore(q->queue_lock, flags);
+}
+
+static void as_update_thinktime(struct as_data *ad, struct as_io_context *aic,
+				unsigned long ttime)
+{
+	/* fixed point: 1.0 == 1<<8 */
+	if (aic->ttime_samples == 0) {
+		ad->new_ttime_total = (7*ad->new_ttime_total + 256*ttime) / 8;
+		ad->new_ttime_mean = ad->new_ttime_total / 256;
+
+		ad->exit_prob = (7*ad->exit_prob)/8;
+	}
+	aic->ttime_samples = (7*aic->ttime_samples + 256) / 8;
+	aic->ttime_total = (7*aic->ttime_total + 256*ttime) / 8;
+	aic->ttime_mean = (aic->ttime_total + 128) / aic->ttime_samples;
+}
+
+static void as_update_seekdist(struct as_data *ad, struct as_io_context *aic,
+				sector_t sdist)
+{
+	u64 total;
+
+	if (aic->seek_samples == 0) {
+		ad->new_seek_total = (7*ad->new_seek_total + 256*(u64)sdist)/8;
+		ad->new_seek_mean = ad->new_seek_total / 256;
+	}
+
+	/*
+	 * Don't allow the seek distance to get too large from the
+	 * odd fragment, pagein, etc
+	 */
+	if (aic->seek_samples <= 60) /* second&third seek */
+		sdist = min(sdist, (aic->seek_mean * 4) + 2*1024*1024);
+	else
+		sdist = min(sdist, (aic->seek_mean * 4)	+ 2*1024*64);
+
+	aic->seek_samples = (7*aic->seek_samples + 256) / 8;
+	aic->seek_total = (7*aic->seek_total + (u64)256*sdist) / 8;
+	total = aic->seek_total + (aic->seek_samples/2);
+	do_div(total, aic->seek_samples);
+	aic->seek_mean = (sector_t)total;
+}
+
+/*
+ * as_update_iohist keeps a decaying histogram of IO thinktimes, and
+ * updates @aic->ttime_mean based on that. It is called when a new
+ * request is queued.
+ */
+static void as_update_iohist(struct as_data *ad, struct as_io_context *aic,
+				struct request *rq)
+{
+	struct as_rq *arq = RQ_DATA(rq);
+	int data_dir = arq->is_sync;
+	unsigned long thinktime = 0;
+	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);
+			}
+			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_close_req decides if one request is considered "close" to the
+ * previous one issued.
+ */
+static int as_close_req(struct as_data *ad, struct as_io_context *aic,
+				struct 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) */
+	sector_t s;
+
+	if (ad->antic_status == ANTIC_OFF || !ad->ioc_finished)
+		delay = 0;
+	else
+		delay = ((jiffies - ad->antic_start) * 1000) / HZ;
+
+	if (delay == 0)
+		delta = 8192;
+	else if (delay <= 20 && delay <= ad->antic_expire)
+		delta = 8192 << delay;
+	else
+		return 1;
+
+	if ((last <= next + (delta>>1)) && (next <= last + delta))
+		return 1;
+
+	if (last < next)
+		s = next - last;
+	else
+		s = last - next;
+
+	if (aic->seek_samples == 0) {
+		/*
+		 * Process has just started IO. Use past statistics to
+		 * gauge success possibility
+		 */
+		if (ad->new_seek_mean > s) {
+			/* this request is better than what we're expecting */
+			return 1;
+		}
+
+	} else {
+		if (aic->seek_mean > s) {
+			/* this request is better than what we're expecting */
+			return 1;
+		}
+	}
+
+	return 0;
+}
+
+/*
+ * as_can_break_anticipation returns true if we have been anticipating this
+ * request.
+ *
+ * It also returns true if the process against which we are anticipating
+ * submits a write - that's presumably an fsync, O_SYNC write, etc. We want to
+ * dispatch it ASAP, because we know that application will not be submitting
+ * any new reads.
+ *
+ * If the task which has submitted the request has exited, break anticipation.
+ *
+ * If this task has queued some other IO, do not enter enticipation.
+ */
+static int as_can_break_anticipation(struct as_data *ad, struct as_rq *arq)
+{
+	struct io_context *ioc;
+	struct as_io_context *aic;
+
+	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 (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, aic, arq)) {
+		/*
+		 * Found a close request that is not one of ours.
+		 *
+		 * This makes close requests from another process update
+		 * our IO history. Is generally useful when there are
+		 * two or more cooperating processes working in the same
+		 * area.
+		 */
+		if (!test_bit(AS_TASK_RUNNING, &aic->state)) {
+			if (aic->ttime_samples == 0)
+				ad->exit_prob = (7*ad->exit_prob + 256)/8;
+
+			ad->exit_no_coop = (7*ad->exit_no_coop)/8;
+		}
+
+		as_update_iohist(ad, aic, arq->request);
+		return 1;
+	}
+
+	if (!test_bit(AS_TASK_RUNNING, &aic->state)) {
+		/* process anticipated on has exited */
+		if (aic->ttime_samples == 0)
+			ad->exit_prob = (7*ad->exit_prob + 256)/8;
+
+		if (ad->exit_no_coop > 128)
+			return 1;
+	}
+
+	if (aic->ttime_samples == 0) {
+		if (ad->new_ttime_mean > ad->antic_expire)
+			return 1;
+		if (ad->exit_prob * ad->exit_no_coop > 128*256)
+			return 1;
+	} else if (aic->ttime_mean > ad->antic_expire) {
+		/* the process thinks too much between requests */
+		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;
+}
+
+/*
+ * 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 %% probability of exiting without a "
+				"cooperating process submitting IO\n",
+				100*ad->exit_no_coop/256);
+	pos += sprintf(page+pos, "%lu ms new thinktime\n", ad->new_ttime_mean);
+	pos += sprintf(page+pos, "%llu sectors new seek distance\n",
+				(unsigned long long)ad->new_seek_mean);
+
+	return pos;
+}
+
+#define SHOW_FUNCTION(__FUNC, __VAR)				\
+static ssize_t __FUNC(struct 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");
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
new file mode 100644
index 00000000000..ecacca9c877
--- /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");
diff --git a/block/deadline-iosched.c b/block/deadline-iosched.c
new file mode 100644
index 00000000000..7929471d7df
--- /dev/null
+++ b/block/deadline-iosched.c
@@ -0,0 +1,878 @@
+/*
+ *  linux/drivers/block/deadline-iosched.c
+ *
+ *  Deadline i/o scheduler.
+ *
+ *  Copyright (C) 2002 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>
+
+/*
+ * See Documentation/block/deadline-iosched.txt
+ */
+static int read_expire = HZ / 2;  /* max time before a read is submitted. */
+static int write_expire = 5 * HZ; /* ditto for writes, these limits are SOFT! */
+static int writes_starved = 2;    /* max times reads can starve a write */
+static int fifo_batch = 16;       /* # of sequential requests treated as one
+				     by the above parameters. For throughput. */
+
+static const int deadline_hash_shift = 5;
+#define DL_HASH_BLOCK(sec)	((sec) >> 3)
+#define DL_HASH_FN(sec)		(hash_long(DL_HASH_BLOCK((sec)), deadline_hash_shift))
+#define DL_HASH_ENTRIES		(1 << deadline_hash_shift)
+#define rq_hash_key(rq)		((rq)->sector + (rq)->nr_sectors)
+#define list_entry_hash(ptr)	list_entry((ptr), struct deadline_rq, hash)
+#define ON_HASH(drq)		(drq)->on_hash
+
+struct deadline_data {
+	/*
+	 * run time data
+	 */
+
+	/*
+	 * requests (deadline_rq s) are present on both sort_list and fifo_list
+	 */
+	struct rb_root sort_list[2];	
+	struct list_head fifo_list[2];
+	
+	/*
+	 * next in sort order. read, write or both are NULL
+	 */
+	struct deadline_rq *next_drq[2];
+	struct list_head *hash;		/* request hash */
+	unsigned int batching;		/* number of sequential requests made */
+	sector_t last_sector;		/* head position */
+	unsigned int starved;		/* times reads have starved writes */
+
+	/*
+	 * settings that change how the i/o scheduler behaves
+	 */
+	int fifo_expire[2];
+	int fifo_batch;
+	int writes_starved;
+	int front_merges;
+
+	mempool_t *drq_pool;
+};
+
+/*
+ * pre-request data.
+ */
+struct deadline_rq {
+	/*
+	 * rbtree index, key is the starting offset
+	 */
+	struct rb_node rb_node;
+	sector_t rb_key;
+
+	struct request *request;
+
+	/*
+	 * request hash, key is the ending offset (for back merge lookup)
+	 */
+	struct list_head hash;
+	char on_hash;
+
+	/*
+	 * expire fifo
+	 */
+	struct list_head fifo;
+	unsigned long expires;
+};
+
+static void deadline_move_request(struct deadline_data *dd, struct deadline_rq *drq);
+
+static kmem_cache_t *drq_pool;
+
+#define RQ_DATA(rq)	((struct deadline_rq *) (rq)->elevator_private)
+
+/*
+ * the back merge hash support functions
+ */
+static inline void __deadline_del_drq_hash(struct deadline_rq *drq)
+{
+	drq->on_hash = 0;
+	list_del_init(&drq->hash);
+}
+
+static inline void deadline_del_drq_hash(struct deadline_rq *drq)
+{
+	if (ON_HASH(drq))
+		__deadline_del_drq_hash(drq);
+}
+
+static inline void
+deadline_add_drq_hash(struct deadline_data *dd, struct deadline_rq *drq)
+{
+	struct request *rq = drq->request;
+
+	BUG_ON(ON_HASH(drq));
+
+	drq->on_hash = 1;
+	list_add(&drq->hash, &dd->hash[DL_HASH_FN(rq_hash_key(rq))]);
+}
+
+/*
+ * move hot entry to front of chain
+ */
+static inline void
+deadline_hot_drq_hash(struct deadline_data *dd, struct deadline_rq *drq)
+{
+	struct request *rq = drq->request;
+	struct list_head *head = &dd->hash[DL_HASH_FN(rq_hash_key(rq))];
+
+	if (ON_HASH(drq) && drq->hash.prev != head) {
+		list_del(&drq->hash);
+		list_add(&drq->hash, head);
+	}
+}
+
+static struct request *
+deadline_find_drq_hash(struct deadline_data *dd, sector_t offset)
+{
+	struct list_head *hash_list = &dd->hash[DL_HASH_FN(offset)];
+	struct list_head *entry, *next = hash_list->next;
+
+	while ((entry = next) != hash_list) {
+		struct deadline_rq *drq = list_entry_hash(entry);
+		struct request *__rq = drq->request;
+
+		next = entry->next;
+		
+		BUG_ON(!ON_HASH(drq));
+
+		if (!rq_mergeable(__rq)) {
+			__deadline_del_drq_hash(drq);
+			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_drq(node)	rb_entry((node), struct deadline_rq, rb_node)
+#define DRQ_RB_ROOT(dd, drq)	(&(dd)->sort_list[rq_data_dir((drq)->request)])
+#define rq_rb_key(rq)		(rq)->sector
+
+static struct deadline_rq *
+__deadline_add_drq_rb(struct deadline_data *dd, struct deadline_rq *drq)
+{
+	struct rb_node **p = &DRQ_RB_ROOT(dd, drq)->rb_node;
+	struct rb_node *parent = NULL;
+	struct deadline_rq *__drq;
+
+	while (*p) {
+		parent = *p;
+		__drq = rb_entry_drq(parent);
+
+		if (drq->rb_key < __drq->rb_key)
+			p = &(*p)->rb_left;
+		else if (drq->rb_key > __drq->rb_key)
+			p = &(*p)->rb_right;
+		else
+			return __drq;
+	}
+
+	rb_link_node(&drq->rb_node, parent, p);
+	return NULL;
+}
+
+static void
+deadline_add_drq_rb(struct deadline_data *dd, struct deadline_rq *drq)
+{
+	struct deadline_rq *__alias;
+
+	drq->rb_key = rq_rb_key(drq->request);
+
+retry:
+	__alias = __deadline_add_drq_rb(dd, drq);
+	if (!__alias) {
+		rb_insert_color(&drq->rb_node, DRQ_RB_ROOT(dd, drq));
+		return;
+	}
+
+	deadline_move_request(dd, __alias);
+	goto retry;
+}
+
+static inline void
+deadline_del_drq_rb(struct deadline_data *dd, struct deadline_rq *drq)
+{
+	const int data_dir = rq_data_dir(drq->request);
+
+	if (dd->next_drq[data_dir] == drq) {
+		struct rb_node *rbnext = rb_next(&drq->rb_node);
+
+		dd->next_drq[data_dir] = NULL;
+		if (rbnext)
+			dd->next_drq[data_dir] = rb_entry_drq(rbnext);
+	}
+
+	BUG_ON(!ON_RB(&drq->rb_node));
+	rb_erase(&drq->rb_node, DRQ_RB_ROOT(dd, drq));
+	RB_CLEAR(&drq->rb_node);
+}
+
+static struct request *
+deadline_find_drq_rb(struct deadline_data *dd, sector_t sector, int data_dir)
+{
+	struct rb_node *n = dd->sort_list[data_dir].rb_node;
+	struct deadline_rq *drq;
+
+	while (n) {
+		drq = rb_entry_drq(n);
+
+		if (sector < drq->rb_key)
+			n = n->rb_left;
+		else if (sector > drq->rb_key)
+			n = n->rb_right;
+		else
+			return drq->request;
+	}
+
+	return NULL;
+}
+
+/*
+ * deadline_find_first_drq 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 deadline_rq *
+deadline_find_first_drq(struct deadline_data *dd, int data_dir)
+{
+	struct rb_node *n = dd->sort_list[data_dir].rb_node;
+
+	for (;;) {
+		if (n->rb_left == NULL)
+			return rb_entry_drq(n);
+		
+		n = n->rb_left;
+	}
+}
+
+/*
+ * add drq to rbtree and fifo
+ */
+static void
+deadline_add_request(struct request_queue *q, struct request *rq)
+{
+	struct deadline_data *dd = q->elevator->elevator_data;
+	struct deadline_rq *drq = RQ_DATA(rq);
+
+	const int data_dir = rq_data_dir(drq->request);
+
+	deadline_add_drq_rb(dd, drq);
+	/*
+	 * set expire time (only used for reads) and add to fifo list
+	 */
+	drq->expires = jiffies + dd->fifo_expire[data_dir];
+	list_add_tail(&drq->fifo, &dd->fifo_list[data_dir]);
+
+	if (rq_mergeable(rq))
+		deadline_add_drq_hash(dd, drq);
+}
+
+/*
+ * remove rq from rbtree, fifo, and hash
+ */
+static void deadline_remove_request(request_queue_t *q, struct request *rq)
+{
+	struct deadline_rq *drq = RQ_DATA(rq);
+	struct deadline_data *dd = q->elevator->elevator_data;
+
+	list_del_init(&drq->fifo);
+	deadline_del_drq_rb(dd, drq);
+	deadline_del_drq_hash(drq);
+}
+
+static int
+deadline_merge(request_queue_t *q, struct request **req, struct bio *bio)
+{
+	struct deadline_data *dd = q->elevator->elevator_data;
+	struct request *__rq;
+	int ret;
+
+	/*
+	 * see if the merge hash can satisfy a back merge
+	 */
+	__rq = deadline_find_drq_hash(dd, 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
+	 */
+	if (dd->front_merges) {
+		sector_t rb_key = bio->bi_sector + bio_sectors(bio);
+
+		__rq = deadline_find_drq_rb(dd, 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)
+		deadline_hot_drq_hash(dd, RQ_DATA(__rq));
+	*req = __rq;
+	return ret;
+}
+
+static void deadline_merged_request(request_queue_t *q, struct request *req)
+{
+	struct deadline_data *dd = q->elevator->elevator_data;
+	struct deadline_rq *drq = RQ_DATA(req);
+
+	/*
+	 * hash always needs to be repositioned, key is end sector
+	 */
+	deadline_del_drq_hash(drq);
+	deadline_add_drq_hash(dd, drq);
+
+	/*
+	 * if the merge was a front merge, we need to reposition request
+	 */
+	if (rq_rb_key(req) != drq->rb_key) {
+		deadline_del_drq_rb(dd, drq);
+		deadline_add_drq_rb(dd, drq);
+	}
+}
+
+static void
+deadline_merged_requests(request_queue_t *q, struct request *req,
+			 struct request *next)
+{
+	struct deadline_data *dd = q->elevator->elevator_data;
+	struct deadline_rq *drq = RQ_DATA(req);
+	struct deadline_rq *dnext = RQ_DATA(next);
+
+	BUG_ON(!drq);
+	BUG_ON(!dnext);
+
+	/*
+	 * reposition drq (this is the merged request) in hash, and in rbtree
+	 * in case of a front merge
+	 */
+	deadline_del_drq_hash(drq);
+	deadline_add_drq_hash(dd, drq);
+
+	if (rq_rb_key(req) != drq->rb_key) {
+		deadline_del_drq_rb(dd, drq);
+		deadline_add_drq_rb(dd, drq);
+	}
+
+	/*
+	 * if dnext expires before drq, assign its expire time to drq
+	 * and move into dnext position (dnext will be deleted) in fifo
+	 */
+	if (!list_empty(&drq->fifo) && !list_empty(&dnext->fifo)) {
+		if (time_before(dnext->expires, drq->expires)) {
+			list_move(&drq->fifo, &dnext->fifo);
+			drq->expires = dnext->expires;
+		}
+	}
+
+	/*
+	 * kill knowledge of next, this one is a goner
+	 */
+	deadline_remove_request(q, next);
+}
+
+/*
+ * move request from sort list to dispatch queue.
+ */
+static inline void
+deadline_move_to_dispatch(struct deadline_data *dd, struct deadline_rq *drq)
+{
+	request_queue_t *q = drq->request->q;
+
+	deadline_remove_request(q, drq->request);
+	elv_dispatch_add_tail(q, drq->request);
+}
+
+/*
+ * move an entry to dispatch queue
+ */
+static void
+deadline_move_request(struct deadline_data *dd, struct deadline_rq *drq)
+{
+	const int data_dir = rq_data_dir(drq->request);
+	struct rb_node *rbnext = rb_next(&drq->rb_node);
+
+	dd->next_drq[READ] = NULL;
+	dd->next_drq[WRITE] = NULL;
+
+	if (rbnext)
+		dd->next_drq[data_dir] = rb_entry_drq(rbnext);
+	
+	dd->last_sector = drq->request->sector + drq->request->nr_sectors;
+
+	/*
+	 * take it off the sort and fifo list, move
+	 * to dispatch queue
+	 */
+	deadline_move_to_dispatch(dd, drq);
+}
+
+#define list_entry_fifo(ptr)	list_entry((ptr), struct deadline_rq, fifo)
+
+/*
+ * deadline_check_fifo returns 0 if there are no expired reads on the fifo,
+ * 1 otherwise. Requires !list_empty(&dd->fifo_list[data_dir])
+ */
+static inline int deadline_check_fifo(struct deadline_data *dd, int ddir)
+{
+	struct deadline_rq *drq = list_entry_fifo(dd->fifo_list[ddir].next);
+
+	/*
+	 * drq is expired!
+	 */
+	if (time_after(jiffies, drq->expires))
+		return 1;
+
+	return 0;
+}
+
+/*
+ * deadline_dispatch_requests selects the best request according to
+ * read/write expire, fifo_batch, etc
+ */
+static int deadline_dispatch_requests(request_queue_t *q, int force)
+{
+	struct deadline_data *dd = q->elevator->elevator_data;
+	const int reads = !list_empty(&dd->fifo_list[READ]);
+	const int writes = !list_empty(&dd->fifo_list[WRITE]);
+	struct deadline_rq *drq;
+	int data_dir;
+
+	/*
+	 * batches are currently reads XOR writes
+	 */
+	if (dd->next_drq[WRITE])
+		drq = dd->next_drq[WRITE];
+	else
+		drq = dd->next_drq[READ];
+
+	if (drq) {
+		/* we have a "next request" */
+		
+		if (dd->last_sector != drq->request->sector)
+			/* end the batch on a non sequential request */
+			dd->batching += dd->fifo_batch;
+		
+		if (dd->batching < dd->fifo_batch)
+			/* we are still entitled to batch */
+			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(&dd->sort_list[READ]));
+
+		if (writes && (dd->starved++ >= dd->writes_starved))
+			goto dispatch_writes;
+
+		data_dir = READ;
+
+		goto dispatch_find_request;
+	}
+
+	/*
+	 * there are either no reads or writes have been starved
+	 */
+
+	if (writes) {
+dispatch_writes:
+		BUG_ON(RB_EMPTY(&dd->sort_list[WRITE]));
+
+		dd->starved = 0;
+
+		data_dir = WRITE;
+
+		goto dispatch_find_request;
+	}
+
+	return 0;
+
+dispatch_find_request:
+	/*
+	 * we are not running a batch, find best request for selected data_dir
+	 */
+	if (deadline_check_fifo(dd, data_dir)) {
+		/* An expired request exists - satisfy it */
+		dd->batching = 0;
+		drq = list_entry_fifo(dd->fifo_list[data_dir].next);
+		
+	} else if (dd->next_drq[data_dir]) {
+		/*
+		 * The last req was the same dir and we have a next request in
+		 * sort order. No expired requests so continue on from here.
+		 */
+		drq = dd->next_drq[data_dir];
+	} else {
+		/*
+		 * The last req was the other direction or we have run out of
+		 * higher-sectored requests. Go back to the lowest sectored
+		 * request (1 way elevator) and start a new batch.
+		 */
+		dd->batching = 0;
+		drq = deadline_find_first_drq(dd, data_dir);
+	}
+
+dispatch_request:
+	/*
+	 * drq is the selected appropriate request.
+	 */
+	dd->batching++;
+	deadline_move_request(dd, drq);
+
+	return 1;
+}
+
+static int deadline_queue_empty(request_queue_t *q)
+{
+	struct deadline_data *dd = q->elevator->elevator_data;
+
+	return list_empty(&dd->fifo_list[WRITE])
+		&& list_empty(&dd->fifo_list[READ]);
+}
+
+static struct request *
+deadline_former_request(request_queue_t *q, struct request *rq)
+{
+	struct deadline_rq *drq = RQ_DATA(rq);
+	struct rb_node *rbprev = rb_prev(&drq->rb_node);
+
+	if (rbprev)
+		return rb_entry_drq(rbprev)->request;
+
+	return NULL;
+}
+
+static struct request *
+deadline_latter_request(request_queue_t *q, struct request *rq)
+{
+	struct deadline_rq *drq = RQ_DATA(rq);
+	struct rb_node *rbnext = rb_next(&drq->rb_node);
+
+	if (rbnext)
+		return rb_entry_drq(rbnext)->request;
+
+	return NULL;
+}
+
+static void deadline_exit_queue(elevator_t *e)
+{
+	struct deadline_data *dd = e->elevator_data;
+
+	BUG_ON(!list_empty(&dd->fifo_list[READ]));
+	BUG_ON(!list_empty(&dd->fifo_list[WRITE]));
+
+	mempool_destroy(dd->drq_pool);
+	kfree(dd->hash);
+	kfree(dd);
+}
+
+/*
+ * initialize elevator private data (deadline_data), and alloc a drq for
+ * each request on the free lists
+ */
+static int deadline_init_queue(request_queue_t *q, elevator_t *e)
+{
+	struct deadline_data *dd;
+	int i;
+
+	if (!drq_pool)
+		return -ENOMEM;
+
+	dd = kmalloc_node(sizeof(*dd), GFP_KERNEL, q->node);
+	if (!dd)
+		return -ENOMEM;
+	memset(dd, 0, sizeof(*dd));
+
+	dd->hash = kmalloc_node(sizeof(struct list_head)*DL_HASH_ENTRIES,
+				GFP_KERNEL, q->node);
+	if (!dd->hash) {
+		kfree(dd);
+		return -ENOMEM;
+	}
+
+	dd->drq_pool = mempool_create_node(BLKDEV_MIN_RQ, mempool_alloc_slab,
+					mempool_free_slab, drq_pool, q->node);
+	if (!dd->drq_pool) {
+		kfree(dd->hash);
+		kfree(dd);
+		return -ENOMEM;
+	}
+
+	for (i = 0; i < DL_HASH_ENTRIES; i++)
+		INIT_LIST_HEAD(&dd->hash[i]);
+
+	INIT_LIST_HEAD(&dd->fifo_list[READ]);
+	INIT_LIST_HEAD(&dd->fifo_list[WRITE]);
+	dd->sort_list[READ] = RB_ROOT;
+	dd->sort_list[WRITE] = RB_ROOT;
+	dd->fifo_expire[READ] = read_expire;
+	dd->fifo_expire[WRITE] = write_expire;
+	dd->writes_starved = writes_starved;
+	dd->front_merges = 1;
+	dd->fifo_batch = fifo_batch;
+	e->elevator_data = dd;
+	return 0;
+}
+
+static void deadline_put_request(request_queue_t *q, struct request *rq)
+{
+	struct deadline_data *dd = q->elevator->elevator_data;
+	struct deadline_rq *drq = RQ_DATA(rq);
+
+	mempool_free(drq, dd->drq_pool);
+	rq->elevator_private = NULL;
+}
+
+static int
+deadline_set_request(request_queue_t *q, struct request *rq, struct bio *bio,
+		     gfp_t gfp_mask)
+{
+	struct deadline_data *dd = q->elevator->elevator_data;
+	struct deadline_rq *drq;
+
+	drq = mempool_alloc(dd->drq_pool, gfp_mask);
+	if (drq) {
+		memset(drq, 0, sizeof(*drq));
+		RB_CLEAR(&drq->rb_node);
+		drq->request = rq;
+
+		INIT_LIST_HEAD(&drq->hash);
+		drq->on_hash = 0;
+
+		INIT_LIST_HEAD(&drq->fifo);
+
+		rq->elevator_private = drq;
+		return 0;
+	}
+
+	return 1;
+}
+
+/*
+ * sysfs parts below
+ */
+struct deadline_fs_entry {
+	struct attribute attr;
+	ssize_t (*show)(struct deadline_data *, char *);
+	ssize_t (*store)(struct deadline_data *, const char *, size_t);
+};
+
+static ssize_t
+deadline_var_show(int var, char *page)
+{
+	return sprintf(page, "%d\n", var);
+}
+
+static ssize_t
+deadline_var_store(int *var, const char *page, size_t count)
+{
+	char *p = (char *) page;
+
+	*var = simple_strtol(p, &p, 10);
+	return count;
+}
+
+#define SHOW_FUNCTION(__FUNC, __VAR, __CONV)				\
+static ssize_t __FUNC(struct deadline_data *dd, char *page)		\
+{									\
+	int __data = __VAR;					\
+	if (__CONV)							\
+		__data = jiffies_to_msecs(__data);			\
+	return deadline_var_show(__data, (page));			\
+}
+SHOW_FUNCTION(deadline_readexpire_show, dd->fifo_expire[READ], 1);
+SHOW_FUNCTION(deadline_writeexpire_show, dd->fifo_expire[WRITE], 1);
+SHOW_FUNCTION(deadline_writesstarved_show, dd->writes_starved, 0);
+SHOW_FUNCTION(deadline_frontmerges_show, dd->front_merges, 0);
+SHOW_FUNCTION(deadline_fifobatch_show, dd->fifo_batch, 0);
+#undef SHOW_FUNCTION
+
+#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV)			\
+static ssize_t __FUNC(struct deadline_data *dd, const char *page, size_t count)	\
+{									\
+	int __data;							\
+	int ret = deadline_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(deadline_readexpire_store, &dd->fifo_expire[READ], 0, INT_MAX, 1);
+STORE_FUNCTION(deadline_writeexpire_store, &dd->fifo_expire[WRITE], 0, INT_MAX, 1);
+STORE_FUNCTION(deadline_writesstarved_store, &dd->writes_starved, INT_MIN, INT_MAX, 0);
+STORE_FUNCTION(deadline_frontmerges_store, &dd->front_merges, 0, 1, 0);
+STORE_FUNCTION(deadline_fifobatch_store, &dd->fifo_batch, 0, INT_MAX, 0);
+#undef STORE_FUNCTION
+
+static struct deadline_fs_entry deadline_readexpire_entry = {
+	.attr = {.name = "read_expire", .mode = S_IRUGO | S_IWUSR },
+	.show = deadline_readexpire_show,
+	.store = deadline_readexpire_store,
+};
+static struct deadline_fs_entry deadline_writeexpire_entry = {
+	.attr = {.name = "write_expire", .mode = S_IRUGO | S_IWUSR },
+	.show = deadline_writeexpire_show,
+	.store = deadline_writeexpire_store,
+};
+static struct deadline_fs_entry deadline_writesstarved_entry = {
+	.attr = {.name = "writes_starved", .mode = S_IRUGO | S_IWUSR },
+	.show = deadline_writesstarved_show,
+	.store = deadline_writesstarved_store,
+};
+static struct deadline_fs_entry deadline_frontmerges_entry = {
+	.attr = {.name = "front_merges", .mode = S_IRUGO | S_IWUSR },
+	.show = deadline_frontmerges_show,
+	.store = deadline_frontmerges_store,
+};
+static struct deadline_fs_entry deadline_fifobatch_entry = {
+	.attr = {.name = "fifo_batch", .mode = S_IRUGO | S_IWUSR },
+	.show = deadline_fifobatch_show,
+	.store = deadline_fifobatch_store,
+};
+
+static struct attribute *default_attrs[] = {
+	&deadline_readexpire_entry.attr,
+	&deadline_writeexpire_entry.attr,
+	&deadline_writesstarved_entry.attr,
+	&deadline_frontmerges_entry.attr,
+	&deadline_fifobatch_entry.attr,
+	NULL,
+};
+
+#define to_deadline(atr) container_of((atr), struct deadline_fs_entry, attr)
+
+static ssize_t
+deadline_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
+{
+	elevator_t *e = container_of(kobj, elevator_t, kobj);
+	struct deadline_fs_entry *entry = to_deadline(attr);
+
+	if (!entry->show)
+		return -EIO;
+
+	return entry->show(e->elevator_data, page);
+}
+
+static ssize_t
+deadline_attr_store(struct kobject *kobj, struct attribute *attr,
+		    const char *page, size_t length)
+{
+	elevator_t *e = container_of(kobj, elevator_t, kobj);
+	struct deadline_fs_entry *entry = to_deadline(attr);
+
+	if (!entry->store)
+		return -EIO;
+
+	return entry->store(e->elevator_data, page, length);
+}
+
+static struct sysfs_ops deadline_sysfs_ops = {
+	.show	= deadline_attr_show,
+	.store	= deadline_attr_store,
+};
+
+static struct kobj_type deadline_ktype = {
+	.sysfs_ops	= &deadline_sysfs_ops,
+	.default_attrs	= default_attrs,
+};
+
+static struct elevator_type iosched_deadline = {
+	.ops = {
+		.elevator_merge_fn = 		deadline_merge,
+		.elevator_merged_fn =		deadline_merged_request,
+		.elevator_merge_req_fn =	deadline_merged_requests,
+		.elevator_dispatch_fn =		deadline_dispatch_requests,
+		.elevator_add_req_fn =		deadline_add_request,
+		.elevator_queue_empty_fn =	deadline_queue_empty,
+		.elevator_former_req_fn =	deadline_former_request,
+		.elevator_latter_req_fn =	deadline_latter_request,
+		.elevator_set_req_fn =		deadline_set_request,
+		.elevator_put_req_fn = 		deadline_put_request,
+		.elevator_init_fn =		deadline_init_queue,
+		.elevator_exit_fn =		deadline_exit_queue,
+	},
+
+	.elevator_ktype = &deadline_ktype,
+	.elevator_name = "deadline",
+	.elevator_owner = THIS_MODULE,
+};
+
+static int __init deadline_init(void)
+{
+	int ret;
+
+	drq_pool = kmem_cache_create("deadline_drq", sizeof(struct deadline_rq),
+				     0, 0, NULL, NULL);
+
+	if (!drq_pool)
+		return -ENOMEM;
+
+	ret = elv_register(&iosched_deadline);
+	if (ret)
+		kmem_cache_destroy(drq_pool);
+
+	return ret;
+}
+
+static void __exit deadline_exit(void)
+{
+	kmem_cache_destroy(drq_pool);
+	elv_unregister(&iosched_deadline);
+}
+
+module_init(deadline_init);
+module_exit(deadline_exit);
+
+MODULE_AUTHOR("Jens Axboe");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("deadline IO scheduler");
diff --git a/block/elevator.c b/block/elevator.c
new file mode 100644
index 00000000000..d4a49a3df82
--- /dev/null
+++ b/block/elevator.c
@@ -0,0 +1,802 @@
+/*
+ *  linux/drivers/block/elevator.c
+ *
+ *  Block device elevator/IO-scheduler.
+ *
+ *  Copyright (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE
+ *
+ * 30042000 Jens Axboe <axboe@suse.de> :
+ *
+ * Split the elevator a bit so that it is possible to choose a different
+ * one or even write a new "plug in". There are three pieces:
+ * - elevator_fn, inserts a new request in the queue list
+ * - elevator_merge_fn, decides whether a new buffer can be merged with
+ *   an existing request
+ * - elevator_dequeue_fn, called when a request is taken off the active list
+ *
+ * 20082000 Dave Jones <davej@suse.de> :
+ * Removed tests for max-bomb-segments, which was breaking elvtune
+ *  when run without -bN
+ *
+ * Jens:
+ * - Rework again to work with bio instead of buffer_heads
+ * - loose bi_dev comparisons, partition handling is right now
+ * - completely modularize elevator setup and teardown
+ *
+ */
+#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/delay.h>
+
+#include <asm/uaccess.h>
+
+static DEFINE_SPINLOCK(elv_list_lock);
+static LIST_HEAD(elv_list);
+
+/*
+ * can we safely merge with this request?
+ */
+inline int elv_rq_merge_ok(struct request *rq, struct bio *bio)
+{
+	if (!rq_mergeable(rq))
+		return 0;
+
+	/*
+	 * different data direction or already started, don't merge
+	 */
+	if (bio_data_dir(bio) != rq_data_dir(rq))
+		return 0;
+
+	/*
+	 * same device and no special stuff set, merge is ok
+	 */
+	if (rq->rq_disk == bio->bi_bdev->bd_disk &&
+	    !rq->waiting && !rq->special)
+		return 1;
+
+	return 0;
+}
+EXPORT_SYMBOL(elv_rq_merge_ok);
+
+inline int elv_try_merge(struct request *__rq, struct bio *bio)
+{
+	int ret = ELEVATOR_NO_MERGE;
+
+	/*
+	 * we can merge and sequence is ok, check if it's possible
+	 */
+	if (elv_rq_merge_ok(__rq, bio)) {
+		if (__rq->sector + __rq->nr_sectors == bio->bi_sector)
+			ret = ELEVATOR_BACK_MERGE;
+		else if (__rq->sector - bio_sectors(bio) == bio->bi_sector)
+			ret = ELEVATOR_FRONT_MERGE;
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL(elv_try_merge);
+
+static struct elevator_type *elevator_find(const char *name)
+{
+	struct elevator_type *e = NULL;
+	struct list_head *entry;
+
+	list_for_each(entry, &elv_list) {
+		struct elevator_type *__e;
+
+		__e = list_entry(entry, struct elevator_type, list);
+
+		if (!strcmp(__e->elevator_name, name)) {
+			e = __e;
+			break;
+		}
+	}
+
+	return e;
+}
+
+static void elevator_put(struct elevator_type *e)
+{
+	module_put(e->elevator_owner);
+}
+
+static struct elevator_type *elevator_get(const char *name)
+{
+	struct elevator_type *e;
+
+	spin_lock_irq(&elv_list_lock);
+
+	e = elevator_find(name);
+	if (e && !try_module_get(e->elevator_owner))
+		e = NULL;
+
+	spin_unlock_irq(&elv_list_lock);
+
+	return e;
+}
+
+static int elevator_attach(request_queue_t *q, struct elevator_type *e,
+			   struct elevator_queue *eq)
+{
+	int ret = 0;
+
+	memset(eq, 0, sizeof(*eq));
+	eq->ops = &e->ops;
+	eq->elevator_type = e;
+
+	q->elevator = eq;
+
+	if (eq->ops->elevator_init_fn)
+		ret = eq->ops->elevator_init_fn(q, eq);
+
+	return ret;
+}
+
+static char chosen_elevator[16];
+
+static void elevator_setup_default(void)
+{
+	struct elevator_type *e;
+
+	/*
+	 * If default has not been set, use the compiled-in selection.
+	 */
+	if (!chosen_elevator[0])
+		strcpy(chosen_elevator, CONFIG_DEFAULT_IOSCHED);
+
+ 	/*
+ 	 * If the given scheduler is not available, fall back to no-op.
+ 	 */
+ 	if (!(e = elevator_find(chosen_elevator)))
+ 		strcpy(chosen_elevator, "noop");
+	elevator_put(e);
+}
+
+static int __init elevator_setup(char *str)
+{
+	strncpy(chosen_elevator, str, sizeof(chosen_elevator) - 1);
+	return 0;
+}
+
+__setup("elevator=", elevator_setup);
+
+int elevator_init(request_queue_t *q, char *name)
+{
+	struct elevator_type *e = NULL;
+	struct elevator_queue *eq;
+	int ret = 0;
+
+	INIT_LIST_HEAD(&q->queue_head);
+	q->last_merge = NULL;
+	q->end_sector = 0;
+	q->boundary_rq = NULL;
+
+	elevator_setup_default();
+
+	if (!name)
+		name = chosen_elevator;
+
+	e = elevator_get(name);
+	if (!e)
+		return -EINVAL;
+
+	eq = kmalloc(sizeof(struct elevator_queue), GFP_KERNEL);
+	if (!eq) {
+		elevator_put(e->elevator_type);
+		return -ENOMEM;
+	}
+
+	ret = elevator_attach(q, e, eq);
+	if (ret) {
+		kfree(eq);
+		elevator_put(e->elevator_type);
+	}
+
+	return ret;
+}
+
+void elevator_exit(elevator_t *e)
+{
+	if (e->ops->elevator_exit_fn)
+		e->ops->elevator_exit_fn(e);
+
+	elevator_put(e->elevator_type);
+	e->elevator_type = NULL;
+	kfree(e);
+}
+
+/*
+ * Insert rq into dispatch queue of q.  Queue lock must be held on
+ * entry.  If sort != 0, rq is sort-inserted; otherwise, rq will be
+ * appended to the dispatch queue.  To be used by specific elevators.
+ */
+void elv_dispatch_sort(request_queue_t *q, struct request *rq)
+{
+	sector_t boundary;
+	struct list_head *entry;
+
+	if (q->last_merge == rq)
+		q->last_merge = NULL;
+
+	boundary = q->end_sector;
+
+	list_for_each_prev(entry, &q->queue_head) {
+		struct request *pos = list_entry_rq(entry);
+
+		if (pos->flags & (REQ_SOFTBARRIER|REQ_HARDBARRIER|REQ_STARTED))
+			break;
+		if (rq->sector >= boundary) {
+			if (pos->sector < boundary)
+				continue;
+		} else {
+			if (pos->sector >= boundary)
+				break;
+		}
+		if (rq->sector >= pos->sector)
+			break;
+	}
+
+	list_add(&rq->queuelist, entry);
+}
+
+int elv_merge(request_queue_t *q, struct request **req, struct bio *bio)
+{
+	elevator_t *e = q->elevator;
+	int ret;
+
+	if (q->last_merge) {
+		ret = elv_try_merge(q->last_merge, bio);
+		if (ret != ELEVATOR_NO_MERGE) {
+			*req = q->last_merge;
+			return ret;
+		}
+	}
+
+	if (e->ops->elevator_merge_fn)
+		return e->ops->elevator_merge_fn(q, req, bio);
+
+	return ELEVATOR_NO_MERGE;
+}
+
+void elv_merged_request(request_queue_t *q, struct request *rq)
+{
+	elevator_t *e = q->elevator;
+
+	if (e->ops->elevator_merged_fn)
+		e->ops->elevator_merged_fn(q, rq);
+
+	q->last_merge = rq;
+}
+
+void elv_merge_requests(request_queue_t *q, struct request *rq,
+			     struct request *next)
+{
+	elevator_t *e = q->elevator;
+
+	if (e->ops->elevator_merge_req_fn)
+		e->ops->elevator_merge_req_fn(q, rq, next);
+
+	q->last_merge = rq;
+}
+
+void elv_requeue_request(request_queue_t *q, struct request *rq)
+{
+	elevator_t *e = q->elevator;
+
+	/*
+	 * it already went through dequeue, we need to decrement the
+	 * in_flight count again
+	 */
+	if (blk_account_rq(rq)) {
+		q->in_flight--;
+		if (blk_sorted_rq(rq) && e->ops->elevator_deactivate_req_fn)
+			e->ops->elevator_deactivate_req_fn(q, rq);
+	}
+
+	rq->flags &= ~REQ_STARTED;
+
+	/*
+	 * if this is the flush, requeue the original instead and drop the flush
+	 */
+	if (rq->flags & REQ_BAR_FLUSH) {
+		clear_bit(QUEUE_FLAG_FLUSH, &q->queue_flags);
+		rq = rq->end_io_data;
+	}
+
+	__elv_add_request(q, rq, ELEVATOR_INSERT_FRONT, 0);
+}
+
+void __elv_add_request(request_queue_t *q, struct request *rq, int where,
+		       int plug)
+{
+	if (rq->flags & (REQ_SOFTBARRIER | REQ_HARDBARRIER)) {
+		/*
+		 * barriers implicitly indicate back insertion
+		 */
+		if (where == ELEVATOR_INSERT_SORT)
+			where = ELEVATOR_INSERT_BACK;
+
+		/*
+		 * this request is scheduling boundary, update end_sector
+		 */
+		if (blk_fs_request(rq)) {
+			q->end_sector = rq_end_sector(rq);
+			q->boundary_rq = rq;
+		}
+	} else if (!(rq->flags & REQ_ELVPRIV) && where == ELEVATOR_INSERT_SORT)
+		where = ELEVATOR_INSERT_BACK;
+
+	if (plug)
+		blk_plug_device(q);
+
+	rq->q = q;
+
+	switch (where) {
+	case ELEVATOR_INSERT_FRONT:
+		rq->flags |= REQ_SOFTBARRIER;
+
+		list_add(&rq->queuelist, &q->queue_head);
+		break;
+
+	case ELEVATOR_INSERT_BACK:
+		rq->flags |= REQ_SOFTBARRIER;
+
+		while (q->elevator->ops->elevator_dispatch_fn(q, 1))
+			;
+		list_add_tail(&rq->queuelist, &q->queue_head);
+		/*
+		 * We kick the queue here for the following reasons.
+		 * - The elevator might have returned NULL previously
+		 *   to delay requests and returned them now.  As the
+		 *   queue wasn't empty before this request, ll_rw_blk
+		 *   won't run the queue on return, resulting in hang.
+		 * - Usually, back inserted requests won't be merged
+		 *   with anything.  There's no point in delaying queue
+		 *   processing.
+		 */
+		blk_remove_plug(q);
+		q->request_fn(q);
+		break;
+
+	case ELEVATOR_INSERT_SORT:
+		BUG_ON(!blk_fs_request(rq));
+		rq->flags |= REQ_SORTED;
+		if (q->last_merge == NULL && rq_mergeable(rq))
+			q->last_merge = rq;
+		/*
+		 * Some ioscheds (cfq) run q->request_fn directly, so
+		 * rq cannot be accessed after calling
+		 * elevator_add_req_fn.
+		 */
+		q->elevator->ops->elevator_add_req_fn(q, rq);
+		break;
+
+	default:
+		printk(KERN_ERR "%s: bad insertion point %d\n",
+		       __FUNCTION__, where);
+		BUG();
+	}
+
+	if (blk_queue_plugged(q)) {
+		int nrq = q->rq.count[READ] + q->rq.count[WRITE]
+			- q->in_flight;
+
+		if (nrq >= q->unplug_thresh)
+			__generic_unplug_device(q);
+	}
+}
+
+void elv_add_request(request_queue_t *q, struct request *rq, int where,
+		     int plug)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(q->queue_lock, flags);
+	__elv_add_request(q, rq, where, plug);
+	spin_unlock_irqrestore(q->queue_lock, flags);
+}
+
+static inline struct request *__elv_next_request(request_queue_t *q)
+{
+	struct request *rq;
+
+	if (unlikely(list_empty(&q->queue_head) &&
+		     !q->elevator->ops->elevator_dispatch_fn(q, 0)))
+		return NULL;
+
+	rq = list_entry_rq(q->queue_head.next);
+
+	/*
+	 * if this is a barrier write and the device has to issue a
+	 * flush sequence to support it, check how far we are
+	 */
+	if (blk_fs_request(rq) && blk_barrier_rq(rq)) {
+		BUG_ON(q->ordered == QUEUE_ORDERED_NONE);
+
+		if (q->ordered == QUEUE_ORDERED_FLUSH &&
+		    !blk_barrier_preflush(rq))
+			rq = blk_start_pre_flush(q, rq);
+	}
+
+	return rq;
+}
+
+struct request *elv_next_request(request_queue_t *q)
+{
+	struct request *rq;
+	int ret;
+
+	while ((rq = __elv_next_request(q)) != NULL) {
+		if (!(rq->flags & REQ_STARTED)) {
+			elevator_t *e = q->elevator;
+
+			/*
+			 * This is the first time the device driver
+			 * sees this request (possibly after
+			 * requeueing).  Notify IO scheduler.
+			 */
+			if (blk_sorted_rq(rq) &&
+			    e->ops->elevator_activate_req_fn)
+				e->ops->elevator_activate_req_fn(q, rq);
+
+			/*
+			 * just mark as started even if we don't start
+			 * it, a request that has been delayed should
+			 * not be passed by new incoming requests
+			 */
+			rq->flags |= REQ_STARTED;
+		}
+
+		if (!q->boundary_rq || q->boundary_rq == rq) {
+			q->end_sector = rq_end_sector(rq);
+			q->boundary_rq = NULL;
+		}
+
+		if ((rq->flags & REQ_DONTPREP) || !q->prep_rq_fn)
+			break;
+
+		ret = q->prep_rq_fn(q, rq);
+		if (ret == BLKPREP_OK) {
+			break;
+		} else if (ret == BLKPREP_DEFER) {
+			/*
+			 * the request may have been (partially) prepped.
+			 * we need to keep this request in the front to
+			 * avoid resource deadlock.  REQ_STARTED will
+			 * prevent other fs requests from passing this one.
+			 */
+			rq = NULL;
+			break;
+		} else if (ret == BLKPREP_KILL) {
+			int nr_bytes = rq->hard_nr_sectors << 9;
+
+			if (!nr_bytes)
+				nr_bytes = rq->data_len;
+
+			blkdev_dequeue_request(rq);
+			rq->flags |= REQ_QUIET;
+			end_that_request_chunk(rq, 0, nr_bytes);
+			end_that_request_last(rq);
+		} else {
+			printk(KERN_ERR "%s: bad return=%d\n", __FUNCTION__,
+								ret);
+			break;
+		}
+	}
+
+	return rq;
+}
+
+void elv_dequeue_request(request_queue_t *q, struct request *rq)
+{
+	BUG_ON(list_empty(&rq->queuelist));
+
+	list_del_init(&rq->queuelist);
+
+	/*
+	 * the time frame between a request being removed from the lists
+	 * and to it is freed is accounted as io that is in progress at
+	 * the driver side.
+	 */
+	if (blk_account_rq(rq))
+		q->in_flight++;
+}
+
+int elv_queue_empty(request_queue_t *q)
+{
+	elevator_t *e = q->elevator;
+
+	if (!list_empty(&q->queue_head))
+		return 0;
+
+	if (e->ops->elevator_queue_empty_fn)
+		return e->ops->elevator_queue_empty_fn(q);
+
+	return 1;
+}
+
+struct request *elv_latter_request(request_queue_t *q, struct request *rq)
+{
+	struct list_head *next;
+
+	elevator_t *e = q->elevator;
+
+	if (e->ops->elevator_latter_req_fn)
+		return e->ops->elevator_latter_req_fn(q, rq);
+
+	next = rq->queuelist.next;
+	if (next != &q->queue_head && next != &rq->queuelist)
+		return list_entry_rq(next);
+
+	return NULL;
+}
+
+struct request *elv_former_request(request_queue_t *q, struct request *rq)
+{
+	struct list_head *prev;
+
+	elevator_t *e = q->elevator;
+
+	if (e->ops->elevator_former_req_fn)
+		return e->ops->elevator_former_req_fn(q, rq);
+
+	prev = rq->queuelist.prev;
+	if (prev != &q->queue_head && prev != &rq->queuelist)
+		return list_entry_rq(prev);
+
+	return NULL;
+}
+
+int elv_set_request(request_queue_t *q, struct request *rq, struct bio *bio,
+		    gfp_t gfp_mask)
+{
+	elevator_t *e = q->elevator;
+
+	if (e->ops->elevator_set_req_fn)
+		return e->ops->elevator_set_req_fn(q, rq, bio, gfp_mask);
+
+	rq->elevator_private = NULL;
+	return 0;
+}
+
+void elv_put_request(request_queue_t *q, struct request *rq)
+{
+	elevator_t *e = q->elevator;
+
+	if (e->ops->elevator_put_req_fn)
+		e->ops->elevator_put_req_fn(q, rq);
+}
+
+int elv_may_queue(request_queue_t *q, int rw, struct bio *bio)
+{
+	elevator_t *e = q->elevator;
+
+	if (e->ops->elevator_may_queue_fn)
+		return e->ops->elevator_may_queue_fn(q, rw, bio);
+
+	return ELV_MQUEUE_MAY;
+}
+
+void elv_completed_request(request_queue_t *q, struct request *rq)
+{
+	elevator_t *e = q->elevator;
+
+	/*
+	 * request is released from the driver, io must be done
+	 */
+	if (blk_account_rq(rq)) {
+		q->in_flight--;
+		if (blk_sorted_rq(rq) && e->ops->elevator_completed_req_fn)
+			e->ops->elevator_completed_req_fn(q, rq);
+	}
+}
+
+int elv_register_queue(struct request_queue *q)
+{
+	elevator_t *e = q->elevator;
+
+	e->kobj.parent = kobject_get(&q->kobj);
+	if (!e->kobj.parent)
+		return -EBUSY;
+
+	snprintf(e->kobj.name, KOBJ_NAME_LEN, "%s", "iosched");
+	e->kobj.ktype = e->elevator_type->elevator_ktype;
+
+	return kobject_register(&e->kobj);
+}
+
+void elv_unregister_queue(struct request_queue *q)
+{
+	if (q) {
+		elevator_t *e = q->elevator;
+		kobject_unregister(&e->kobj);
+		kobject_put(&q->kobj);
+	}
+}
+
+int elv_register(struct elevator_type *e)
+{
+	spin_lock_irq(&elv_list_lock);
+	if (elevator_find(e->elevator_name))
+		BUG();
+	list_add_tail(&e->list, &elv_list);
+	spin_unlock_irq(&elv_list_lock);
+
+	printk(KERN_INFO "io scheduler %s registered", e->elevator_name);
+	if (!strcmp(e->elevator_name, chosen_elevator))
+		printk(" (default)");
+	printk("\n");
+	return 0;
+}
+EXPORT_SYMBOL_GPL(elv_register);
+
+void elv_unregister(struct elevator_type *e)
+{
+	struct task_struct *g, *p;
+
+	/*
+	 * Iterate every thread in the process to remove the io contexts.
+	 */
+	read_lock(&tasklist_lock);
+	do_each_thread(g, p) {
+		struct io_context *ioc = p->io_context;
+		if (ioc && ioc->cic) {
+			ioc->cic->exit(ioc->cic);
+			ioc->cic->dtor(ioc->cic);
+			ioc->cic = NULL;
+		}
+		if (ioc && ioc->aic) {
+			ioc->aic->exit(ioc->aic);
+			ioc->aic->dtor(ioc->aic);
+			ioc->aic = NULL;
+		}
+	} while_each_thread(g, p);
+	read_unlock(&tasklist_lock);
+
+	spin_lock_irq(&elv_list_lock);
+	list_del_init(&e->list);
+	spin_unlock_irq(&elv_list_lock);
+}
+EXPORT_SYMBOL_GPL(elv_unregister);
+
+/*
+ * switch to new_e io scheduler. be careful not to introduce deadlocks -
+ * we don't free the old io scheduler, before we have allocated what we
+ * need for the new one. this way we have a chance of going back to the old
+ * one, if the new one fails init for some reason.
+ */
+static void elevator_switch(request_queue_t *q, struct elevator_type *new_e)
+{
+	elevator_t *old_elevator, *e;
+
+	/*
+	 * Allocate new elevator
+	 */
+	e = kmalloc(sizeof(elevator_t), GFP_KERNEL);
+	if (!e)
+		goto error;
+
+	/*
+	 * Turn on BYPASS and drain all requests w/ elevator private data
+	 */
+	spin_lock_irq(q->queue_lock);
+
+	set_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
+
+	while (q->elevator->ops->elevator_dispatch_fn(q, 1))
+		;
+
+	while (q->rq.elvpriv) {
+		spin_unlock_irq(q->queue_lock);
+		msleep(10);
+		spin_lock_irq(q->queue_lock);
+	}
+
+	spin_unlock_irq(q->queue_lock);
+
+	/*
+	 * unregister old elevator data
+	 */
+	elv_unregister_queue(q);
+	old_elevator = q->elevator;
+
+	/*
+	 * attach and start new elevator
+	 */
+	if (elevator_attach(q, new_e, e))
+		goto fail;
+
+	if (elv_register_queue(q))
+		goto fail_register;
+
+	/*
+	 * finally exit old elevator and turn off BYPASS.
+	 */
+	elevator_exit(old_elevator);
+	clear_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
+	return;
+
+fail_register:
+	/*
+	 * switch failed, exit the new io scheduler and reattach the old
+	 * one again (along with re-adding the sysfs dir)
+	 */
+	elevator_exit(e);
+	e = NULL;
+fail:
+	q->elevator = old_elevator;
+	elv_register_queue(q);
+	clear_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
+	kfree(e);
+error:
+	elevator_put(new_e);
+	printk(KERN_ERR "elevator: switch to %s failed\n",new_e->elevator_name);
+}
+
+ssize_t elv_iosched_store(request_queue_t *q, const char *name, size_t count)
+{
+	char elevator_name[ELV_NAME_MAX];
+	struct elevator_type *e;
+
+	memset(elevator_name, 0, sizeof(elevator_name));
+	strncpy(elevator_name, name, sizeof(elevator_name));
+
+	if (elevator_name[strlen(elevator_name) - 1] == '\n')
+		elevator_name[strlen(elevator_name) - 1] = '\0';
+
+	e = elevator_get(elevator_name);
+	if (!e) {
+		printk(KERN_ERR "elevator: type %s not found\n", elevator_name);
+		return -EINVAL;
+	}
+
+	if (!strcmp(elevator_name, q->elevator->elevator_type->elevator_name)) {
+		elevator_put(e);
+		return count;
+	}
+
+	elevator_switch(q, e);
+	return count;
+}
+
+ssize_t elv_iosched_show(request_queue_t *q, char *name)
+{
+	elevator_t *e = q->elevator;
+	struct elevator_type *elv = e->elevator_type;
+	struct list_head *entry;
+	int len = 0;
+
+	spin_lock_irq(q->queue_lock);
+	list_for_each(entry, &elv_list) {
+		struct elevator_type *__e;
+
+		__e = list_entry(entry, struct elevator_type, list);
+		if (!strcmp(elv->elevator_name, __e->elevator_name))
+			len += sprintf(name+len, "[%s] ", elv->elevator_name);
+		else
+			len += sprintf(name+len, "%s ", __e->elevator_name);
+	}
+	spin_unlock_irq(q->queue_lock);
+
+	len += sprintf(len+name, "\n");
+	return len;
+}
+
+EXPORT_SYMBOL(elv_dispatch_sort);
+EXPORT_SYMBOL(elv_add_request);
+EXPORT_SYMBOL(__elv_add_request);
+EXPORT_SYMBOL(elv_requeue_request);
+EXPORT_SYMBOL(elv_next_request);
+EXPORT_SYMBOL(elv_dequeue_request);
+EXPORT_SYMBOL(elv_queue_empty);
+EXPORT_SYMBOL(elv_completed_request);
+EXPORT_SYMBOL(elevator_exit);
+EXPORT_SYMBOL(elevator_init);
diff --git a/block/genhd.c b/block/genhd.c
new file mode 100644
index 00000000000..54aec4a1ae1
--- /dev/null
+++ b/block/genhd.c
@@ -0,0 +1,726 @@
+/*
+ *  gendisk handling
+ */
+
+#include <linux/config.h>
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/genhd.h>
+#include <linux/kernel.h>
+#include <linux/blkdev.h>
+#include <linux/init.h>
+#include <linux/spinlock.h>
+#include <linux/seq_file.h>
+#include <linux/slab.h>
+#include <linux/kmod.h>
+#include <linux/kobj_map.h>
+#include <linux/buffer_head.h>
+
+#define MAX_PROBE_HASH 255	/* random */
+
+static struct subsystem block_subsys;
+
+static DECLARE_MUTEX(block_subsys_sem);
+
+/*
+ * Can be deleted altogether. Later.
+ *
+ */
+static struct blk_major_name {
+	struct blk_major_name *next;
+	int major;
+	char name[16];
+} *major_names[MAX_PROBE_HASH];
+
+/* index in the above - for now: assume no multimajor ranges */
+static inline int major_to_index(int major)
+{
+	return major % MAX_PROBE_HASH;
+}
+
+#ifdef CONFIG_PROC_FS
+/* get block device names in somewhat random order */
+int get_blkdev_list(char *p, int used)
+{
+	struct blk_major_name *n;
+	int i, len;
+
+	len = snprintf(p, (PAGE_SIZE-used), "\nBlock devices:\n");
+
+	down(&block_subsys_sem);
+	for (i = 0; i < ARRAY_SIZE(major_names); i++) {
+		for (n = major_names[i]; n; n = n->next) {
+			/*
+			 * If the curent string plus the 5 extra characters
+			 * in the line would run us off the page, then we're done
+			 */
+			if ((len + used + strlen(n->name) + 5) >= PAGE_SIZE)
+				goto page_full;
+			len += sprintf(p+len, "%3d %s\n",
+				       n->major, n->name);
+		}
+	}
+page_full:
+	up(&block_subsys_sem);
+
+	return len;
+}
+#endif
+
+int register_blkdev(unsigned int major, const char *name)
+{
+	struct blk_major_name **n, *p;
+	int index, ret = 0;
+
+	down(&block_subsys_sem);
+
+	/* temporary */
+	if (major == 0) {
+		for (index = ARRAY_SIZE(major_names)-1; index > 0; index--) {
+			if (major_names[index] == NULL)
+				break;
+		}
+
+		if (index == 0) {
+			printk("register_blkdev: failed to get major for %s\n",
+			       name);
+			ret = -EBUSY;
+			goto out;
+		}
+		major = index;
+		ret = major;
+	}
+
+	p = kmalloc(sizeof(struct blk_major_name), GFP_KERNEL);
+	if (p == NULL) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	p->major = major;
+	strlcpy(p->name, name, sizeof(p->name));
+	p->next = NULL;
+	index = major_to_index(major);
+
+	for (n = &major_names[index]; *n; n = &(*n)->next) {
+		if ((*n)->major == major)
+			break;
+	}
+	if (!*n)
+		*n = p;
+	else
+		ret = -EBUSY;
+
+	if (ret < 0) {
+		printk("register_blkdev: cannot get major %d for %s\n",
+		       major, name);
+		kfree(p);
+	}
+out:
+	up(&block_subsys_sem);
+	return ret;
+}
+
+EXPORT_SYMBOL(register_blkdev);
+
+/* todo: make void - error printk here */
+int unregister_blkdev(unsigned int major, const char *name)
+{
+	struct blk_major_name **n;
+	struct blk_major_name *p = NULL;
+	int index = major_to_index(major);
+	int ret = 0;
+
+	down(&block_subsys_sem);
+	for (n = &major_names[index]; *n; n = &(*n)->next)
+		if ((*n)->major == major)
+			break;
+	if (!*n || strcmp((*n)->name, name))
+		ret = -EINVAL;
+	else {
+		p = *n;
+		*n = p->next;
+	}
+	up(&block_subsys_sem);
+	kfree(p);
+
+	return ret;
+}
+
+EXPORT_SYMBOL(unregister_blkdev);
+
+static struct kobj_map *bdev_map;
+
+/*
+ * Register device numbers dev..(dev+range-1)
+ * range must be nonzero
+ * The hash chain is sorted on range, so that subranges can override.
+ */
+void blk_register_region(dev_t dev, unsigned long range, struct module *module,
+			 struct kobject *(*probe)(dev_t, int *, void *),
+			 int (*lock)(dev_t, void *), void *data)
+{
+	kobj_map(bdev_map, dev, range, module, probe, lock, data);
+}
+
+EXPORT_SYMBOL(blk_register_region);
+
+void blk_unregister_region(dev_t dev, unsigned long range)
+{
+	kobj_unmap(bdev_map, dev, range);
+}
+
+EXPORT_SYMBOL(blk_unregister_region);
+
+static struct kobject *exact_match(dev_t dev, int *part, void *data)
+{
+	struct gendisk *p = data;
+	return &p->kobj;
+}
+
+static int exact_lock(dev_t dev, void *data)
+{
+	struct gendisk *p = data;
+
+	if (!get_disk(p))
+		return -1;
+	return 0;
+}
+
+/**
+ * add_disk - add partitioning information to kernel list
+ * @disk: per-device partitioning information
+ *
+ * This function registers the partitioning information in @disk
+ * with the kernel.
+ */
+void add_disk(struct gendisk *disk)
+{
+	disk->flags |= GENHD_FL_UP;
+	blk_register_region(MKDEV(disk->major, disk->first_minor),
+			    disk->minors, NULL, exact_match, exact_lock, disk);
+	register_disk(disk);
+	blk_register_queue(disk);
+}
+
+EXPORT_SYMBOL(add_disk);
+EXPORT_SYMBOL(del_gendisk);	/* in partitions/check.c */
+
+void unlink_gendisk(struct gendisk *disk)
+{
+	blk_unregister_queue(disk);
+	blk_unregister_region(MKDEV(disk->major, disk->first_minor),
+			      disk->minors);
+}
+
+#define to_disk(obj) container_of(obj,struct gendisk,kobj)
+
+/**
+ * get_gendisk - get partitioning information for a given device
+ * @dev: device to get partitioning information for
+ *
+ * This function gets the structure containing partitioning
+ * information for the given device @dev.
+ */
+struct gendisk *get_gendisk(dev_t dev, int *part)
+{
+	struct kobject *kobj = kobj_lookup(bdev_map, dev, part);
+	return  kobj ? to_disk(kobj) : NULL;
+}
+
+#ifdef CONFIG_PROC_FS
+/* iterator */
+static void *part_start(struct seq_file *part, loff_t *pos)
+{
+	struct list_head *p;
+	loff_t l = *pos;
+
+	down(&block_subsys_sem);
+	list_for_each(p, &block_subsys.kset.list)
+		if (!l--)
+			return list_entry(p, struct gendisk, kobj.entry);
+	return NULL;
+}
+
+static void *part_next(struct seq_file *part, void *v, loff_t *pos)
+{
+	struct list_head *p = ((struct gendisk *)v)->kobj.entry.next;
+	++*pos;
+	return p==&block_subsys.kset.list ? NULL : 
+		list_entry(p, struct gendisk, kobj.entry);
+}
+
+static void part_stop(struct seq_file *part, void *v)
+{
+	up(&block_subsys_sem);
+}
+
+static int show_partition(struct seq_file *part, void *v)
+{
+	struct gendisk *sgp = v;
+	int n;
+	char buf[BDEVNAME_SIZE];
+
+	if (&sgp->kobj.entry == block_subsys.kset.list.next)
+		seq_puts(part, "major minor  #blocks  name\n\n");
+
+	/* Don't show non-partitionable removeable devices or empty devices */
+	if (!get_capacity(sgp) ||
+			(sgp->minors == 1 && (sgp->flags & GENHD_FL_REMOVABLE)))
+		return 0;
+	if (sgp->flags & GENHD_FL_SUPPRESS_PARTITION_INFO)
+		return 0;
+
+	/* show the full disk and all non-0 size partitions of it */
+	seq_printf(part, "%4d  %4d %10llu %s\n",
+		sgp->major, sgp->first_minor,
+		(unsigned long long)get_capacity(sgp) >> 1,
+		disk_name(sgp, 0, buf));
+	for (n = 0; n < sgp->minors - 1; n++) {
+		if (!sgp->part[n])
+			continue;
+		if (sgp->part[n]->nr_sects == 0)
+			continue;
+		seq_printf(part, "%4d  %4d %10llu %s\n",
+			sgp->major, n + 1 + sgp->first_minor,
+			(unsigned long long)sgp->part[n]->nr_sects >> 1 ,
+			disk_name(sgp, n + 1, buf));
+	}
+
+	return 0;
+}
+
+struct seq_operations partitions_op = {
+	.start =part_start,
+	.next =	part_next,
+	.stop =	part_stop,
+	.show =	show_partition
+};
+#endif
+
+
+extern int blk_dev_init(void);
+
+static struct kobject *base_probe(dev_t dev, int *part, void *data)
+{
+	if (request_module("block-major-%d-%d", MAJOR(dev), MINOR(dev)) > 0)
+		/* Make old-style 2.4 aliases work */
+		request_module("block-major-%d", MAJOR(dev));
+	return NULL;
+}
+
+static int __init genhd_device_init(void)
+{
+	bdev_map = kobj_map_init(base_probe, &block_subsys_sem);
+	blk_dev_init();
+	subsystem_register(&block_subsys);
+	return 0;
+}
+
+subsys_initcall(genhd_device_init);
+
+
+
+/*
+ * kobject & sysfs bindings for block devices
+ */
+static ssize_t disk_attr_show(struct kobject *kobj, struct attribute *attr,
+			      char *page)
+{
+	struct gendisk *disk = to_disk(kobj);
+	struct disk_attribute *disk_attr =
+		container_of(attr,struct disk_attribute,attr);
+	ssize_t ret = -EIO;
+
+	if (disk_attr->show)
+		ret = disk_attr->show(disk,page);
+	return ret;
+}
+
+static ssize_t disk_attr_store(struct kobject * kobj, struct attribute * attr,
+			       const char *page, size_t count)
+{
+	struct gendisk *disk = to_disk(kobj);
+	struct disk_attribute *disk_attr =
+		container_of(attr,struct disk_attribute,attr);
+	ssize_t ret = 0;
+
+	if (disk_attr->store)
+		ret = disk_attr->store(disk, page, count);
+	return ret;
+}
+
+static struct sysfs_ops disk_sysfs_ops = {
+	.show	= &disk_attr_show,
+	.store	= &disk_attr_store,
+};
+
+static ssize_t disk_uevent_store(struct gendisk * disk,
+				 const char *buf, size_t count)
+{
+	kobject_hotplug(&disk->kobj, KOBJ_ADD);
+	return count;
+}
+static ssize_t disk_dev_read(struct gendisk * disk, char *page)
+{
+	dev_t base = MKDEV(disk->major, disk->first_minor); 
+	return print_dev_t(page, base);
+}
+static ssize_t disk_range_read(struct gendisk * disk, char *page)
+{
+	return sprintf(page, "%d\n", disk->minors);
+}
+static ssize_t disk_removable_read(struct gendisk * disk, char *page)
+{
+	return sprintf(page, "%d\n",
+		       (disk->flags & GENHD_FL_REMOVABLE ? 1 : 0));
+
+}
+static ssize_t disk_size_read(struct gendisk * disk, char *page)
+{
+	return sprintf(page, "%llu\n", (unsigned long long)get_capacity(disk));
+}
+
+static ssize_t disk_stats_read(struct gendisk * disk, char *page)
+{
+	preempt_disable();
+	disk_round_stats(disk);
+	preempt_enable();
+	return sprintf(page,
+		"%8u %8u %8llu %8u "
+		"%8u %8u %8llu %8u "
+		"%8u %8u %8u"
+		"\n",
+		disk_stat_read(disk, ios[0]), disk_stat_read(disk, merges[0]),
+		(unsigned long long)disk_stat_read(disk, sectors[0]),
+		jiffies_to_msecs(disk_stat_read(disk, ticks[0])),
+		disk_stat_read(disk, ios[1]), disk_stat_read(disk, merges[1]),
+		(unsigned long long)disk_stat_read(disk, sectors[1]),
+		jiffies_to_msecs(disk_stat_read(disk, ticks[1])),
+		disk->in_flight,
+		jiffies_to_msecs(disk_stat_read(disk, io_ticks)),
+		jiffies_to_msecs(disk_stat_read(disk, time_in_queue)));
+}
+static struct disk_attribute disk_attr_uevent = {
+	.attr = {.name = "uevent", .mode = S_IWUSR },
+	.store	= disk_uevent_store
+};
+static struct disk_attribute disk_attr_dev = {
+	.attr = {.name = "dev", .mode = S_IRUGO },
+	.show	= disk_dev_read
+};
+static struct disk_attribute disk_attr_range = {
+	.attr = {.name = "range", .mode = S_IRUGO },
+	.show	= disk_range_read
+};
+static struct disk_attribute disk_attr_removable = {
+	.attr = {.name = "removable", .mode = S_IRUGO },
+	.show	= disk_removable_read
+};
+static struct disk_attribute disk_attr_size = {
+	.attr = {.name = "size", .mode = S_IRUGO },
+	.show	= disk_size_read
+};
+static struct disk_attribute disk_attr_stat = {
+	.attr = {.name = "stat", .mode = S_IRUGO },
+	.show	= disk_stats_read
+};
+
+static struct attribute * default_attrs[] = {
+	&disk_attr_uevent.attr,
+	&disk_attr_dev.attr,
+	&disk_attr_range.attr,
+	&disk_attr_removable.attr,
+	&disk_attr_size.attr,
+	&disk_attr_stat.attr,
+	NULL,
+};
+
+static void disk_release(struct kobject * kobj)
+{
+	struct gendisk *disk = to_disk(kobj);
+	kfree(disk->random);
+	kfree(disk->part);
+	free_disk_stats(disk);
+	kfree(disk);
+}
+
+static struct kobj_type ktype_block = {
+	.release	= disk_release,
+	.sysfs_ops	= &disk_sysfs_ops,
+	.default_attrs	= default_attrs,
+};
+
+extern struct kobj_type ktype_part;
+
+static int block_hotplug_filter(struct kset *kset, struct kobject *kobj)
+{
+	struct kobj_type *ktype = get_ktype(kobj);
+
+	return ((ktype == &ktype_block) || (ktype == &ktype_part));
+}
+
+static int block_hotplug(struct kset *kset, struct kobject *kobj, char **envp,
+			 int num_envp, char *buffer, int buffer_size)
+{
+	struct kobj_type *ktype = get_ktype(kobj);
+	struct device *physdev;
+	struct gendisk *disk;
+	struct hd_struct *part;
+	int length = 0;
+	int i = 0;
+
+	if (ktype == &ktype_block) {
+		disk = container_of(kobj, struct gendisk, kobj);
+		add_hotplug_env_var(envp, num_envp, &i, buffer, buffer_size,
+				    &length, "MINOR=%u", disk->first_minor);
+	} else if (ktype == &ktype_part) {
+		disk = container_of(kobj->parent, struct gendisk, kobj);
+		part = container_of(kobj, struct hd_struct, kobj);
+		add_hotplug_env_var(envp, num_envp, &i, buffer, buffer_size,
+				    &length, "MINOR=%u",
+				    disk->first_minor + part->partno);
+	} else
+		return 0;
+
+	add_hotplug_env_var(envp, num_envp, &i, buffer, buffer_size, &length,
+			    "MAJOR=%u", disk->major);
+
+	/* add physical device, backing this device  */
+	physdev = disk->driverfs_dev;
+	if (physdev) {
+		char *path = kobject_get_path(&physdev->kobj, GFP_KERNEL);
+
+		add_hotplug_env_var(envp, num_envp, &i, buffer, buffer_size,
+				    &length, "PHYSDEVPATH=%s", path);
+		kfree(path);
+
+		if (physdev->bus)
+			add_hotplug_env_var(envp, num_envp, &i,
+					    buffer, buffer_size, &length,
+					    "PHYSDEVBUS=%s",
+					    physdev->bus->name);
+
+		if (physdev->driver)
+			add_hotplug_env_var(envp, num_envp, &i,
+					    buffer, buffer_size, &length,
+					    "PHYSDEVDRIVER=%s",
+					    physdev->driver->name);
+	}
+
+	/* terminate, set to next free slot, shrink available space */
+	envp[i] = NULL;
+	envp = &envp[i];
+	num_envp -= i;
+	buffer = &buffer[length];
+	buffer_size -= length;
+
+	return 0;
+}
+
+static struct kset_hotplug_ops block_hotplug_ops = {
+	.filter		= block_hotplug_filter,
+	.hotplug	= block_hotplug,
+};
+
+/* declare block_subsys. */
+static decl_subsys(block, &ktype_block, &block_hotplug_ops);
+
+
+/*
+ * aggregate disk stat collector.  Uses the same stats that the sysfs
+ * entries do, above, but makes them available through one seq_file.
+ * Watching a few disks may be efficient through sysfs, but watching
+ * all of them will be more efficient through this interface.
+ *
+ * The output looks suspiciously like /proc/partitions with a bunch of
+ * extra fields.
+ */
+
+/* iterator */
+static void *diskstats_start(struct seq_file *part, loff_t *pos)
+{
+	loff_t k = *pos;
+	struct list_head *p;
+
+	down(&block_subsys_sem);
+	list_for_each(p, &block_subsys.kset.list)
+		if (!k--)
+			return list_entry(p, struct gendisk, kobj.entry);
+	return NULL;
+}
+
+static void *diskstats_next(struct seq_file *part, void *v, loff_t *pos)
+{
+	struct list_head *p = ((struct gendisk *)v)->kobj.entry.next;
+	++*pos;
+	return p==&block_subsys.kset.list ? NULL :
+		list_entry(p, struct gendisk, kobj.entry);
+}
+
+static void diskstats_stop(struct seq_file *part, void *v)
+{
+	up(&block_subsys_sem);
+}
+
+static int diskstats_show(struct seq_file *s, void *v)
+{
+	struct gendisk *gp = v;
+	char buf[BDEVNAME_SIZE];
+	int n = 0;
+
+	/*
+	if (&sgp->kobj.entry == block_subsys.kset.list.next)
+		seq_puts(s,	"major minor name"
+				"     rio rmerge rsect ruse wio wmerge "
+				"wsect wuse running use aveq"
+				"\n\n");
+	*/
+ 
+	preempt_disable();
+	disk_round_stats(gp);
+	preempt_enable();
+	seq_printf(s, "%4d %4d %s %u %u %llu %u %u %u %llu %u %u %u %u\n",
+		gp->major, n + gp->first_minor, disk_name(gp, n, buf),
+		disk_stat_read(gp, ios[0]), disk_stat_read(gp, merges[0]),
+		(unsigned long long)disk_stat_read(gp, sectors[0]),
+		jiffies_to_msecs(disk_stat_read(gp, ticks[0])),
+		disk_stat_read(gp, ios[1]), disk_stat_read(gp, merges[1]),
+		(unsigned long long)disk_stat_read(gp, sectors[1]),
+		jiffies_to_msecs(disk_stat_read(gp, ticks[1])),
+		gp->in_flight,
+		jiffies_to_msecs(disk_stat_read(gp, io_ticks)),
+		jiffies_to_msecs(disk_stat_read(gp, time_in_queue)));
+
+	/* now show all non-0 size partitions of it */
+	for (n = 0; n < gp->minors - 1; n++) {
+		struct hd_struct *hd = gp->part[n];
+
+		if (hd && hd->nr_sects)
+			seq_printf(s, "%4d %4d %s %u %u %u %u\n",
+				gp->major, n + gp->first_minor + 1,
+				disk_name(gp, n + 1, buf),
+				hd->ios[0], hd->sectors[0],
+				hd->ios[1], hd->sectors[1]);
+	}
+ 
+	return 0;
+}
+
+struct seq_operations diskstats_op = {
+	.start	= diskstats_start,
+	.next	= diskstats_next,
+	.stop	= diskstats_stop,
+	.show	= diskstats_show
+};
+
+struct gendisk *alloc_disk(int minors)
+{
+	return alloc_disk_node(minors, -1);
+}
+
+struct gendisk *alloc_disk_node(int minors, int node_id)
+{
+	struct gendisk *disk;
+
+	disk = kmalloc_node(sizeof(struct gendisk), GFP_KERNEL, node_id);
+	if (disk) {
+		memset(disk, 0, sizeof(struct gendisk));
+		if (!init_disk_stats(disk)) {
+			kfree(disk);
+			return NULL;
+		}
+		if (minors > 1) {
+			int size = (minors - 1) * sizeof(struct hd_struct *);
+			disk->part = kmalloc_node(size, GFP_KERNEL, node_id);
+			if (!disk->part) {
+				kfree(disk);
+				return NULL;
+			}
+			memset(disk->part, 0, size);
+		}
+		disk->minors = minors;
+		kobj_set_kset_s(disk,block_subsys);
+		kobject_init(&disk->kobj);
+		rand_initialize_disk(disk);
+	}
+	return disk;
+}
+
+EXPORT_SYMBOL(alloc_disk);
+EXPORT_SYMBOL(alloc_disk_node);
+
+struct kobject *get_disk(struct gendisk *disk)
+{
+	struct module *owner;
+	struct kobject *kobj;
+
+	if (!disk->fops)
+		return NULL;
+	owner = disk->fops->owner;
+	if (owner && !try_module_get(owner))
+		return NULL;
+	kobj = kobject_get(&disk->kobj);
+	if (kobj == NULL) {
+		module_put(owner);
+		return NULL;
+	}
+	return kobj;
+
+}
+
+EXPORT_SYMBOL(get_disk);
+
+void put_disk(struct gendisk *disk)
+{
+	if (disk)
+		kobject_put(&disk->kobj);
+}
+
+EXPORT_SYMBOL(put_disk);
+
+void set_device_ro(struct block_device *bdev, int flag)
+{
+	if (bdev->bd_contains != bdev)
+		bdev->bd_part->policy = flag;
+	else
+		bdev->bd_disk->policy = flag;
+}
+
+EXPORT_SYMBOL(set_device_ro);
+
+void set_disk_ro(struct gendisk *disk, int flag)
+{
+	int i;
+	disk->policy = flag;
+	for (i = 0; i < disk->minors - 1; i++)
+		if (disk->part[i]) disk->part[i]->policy = flag;
+}
+
+EXPORT_SYMBOL(set_disk_ro);
+
+int bdev_read_only(struct block_device *bdev)
+{
+	if (!bdev)
+		return 0;
+	else if (bdev->bd_contains != bdev)
+		return bdev->bd_part->policy;
+	else
+		return bdev->bd_disk->policy;
+}
+
+EXPORT_SYMBOL(bdev_read_only);
+
+int invalidate_partition(struct gendisk *disk, int index)
+{
+	int res = 0;
+	struct block_device *bdev = bdget_disk(disk, index);
+	if (bdev) {
+		fsync_bdev(bdev);
+		res = __invalidate_device(bdev);
+		bdput(bdev);
+	}
+	return res;
+}
+
+EXPORT_SYMBOL(invalidate_partition);
diff --git a/block/ioctl.c b/block/ioctl.c
new file mode 100644
index 00000000000..6e278474f9a
--- /dev/null
+++ b/block/ioctl.c
@@ -0,0 +1,275 @@
+#include <linux/sched.h>		/* for capable() */
+#include <linux/blkdev.h>
+#include <linux/blkpg.h>
+#include <linux/backing-dev.h>
+#include <linux/buffer_head.h>
+#include <linux/smp_lock.h>
+#include <asm/uaccess.h>
+
+static int blkpg_ioctl(struct block_device *bdev, struct blkpg_ioctl_arg __user *arg)
+{
+	struct block_device *bdevp;
+	struct gendisk *disk;
+	struct blkpg_ioctl_arg a;
+	struct blkpg_partition p;
+	long long start, length;
+	int part;
+	int i;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EACCES;
+	if (copy_from_user(&a, arg, sizeof(struct blkpg_ioctl_arg)))
+		return -EFAULT;
+	if (copy_from_user(&p, a.data, sizeof(struct blkpg_partition)))
+		return -EFAULT;
+	disk = bdev->bd_disk;
+	if (bdev != bdev->bd_contains)
+		return -EINVAL;
+	part = p.pno;
+	if (part <= 0 || part >= disk->minors)
+		return -EINVAL;
+	switch (a.op) {
+		case BLKPG_ADD_PARTITION:
+			start = p.start >> 9;
+			length = p.length >> 9;
+			/* check for fit in a hd_struct */ 
+			if (sizeof(sector_t) == sizeof(long) && 
+			    sizeof(long long) > sizeof(long)) {
+				long pstart = start, plength = length;
+				if (pstart != start || plength != length
+				    || pstart < 0 || plength < 0)
+					return -EINVAL;
+			}
+			/* partition number in use? */
+			down(&bdev->bd_sem);
+			if (disk->part[part - 1]) {
+				up(&bdev->bd_sem);
+				return -EBUSY;
+			}
+			/* overlap? */
+			for (i = 0; i < disk->minors - 1; i++) {
+				struct hd_struct *s = disk->part[i];
+
+				if (!s)
+					continue;
+				if (!(start+length <= s->start_sect ||
+				      start >= s->start_sect + s->nr_sects)) {
+					up(&bdev->bd_sem);
+					return -EBUSY;
+				}
+			}
+			/* all seems OK */
+			add_partition(disk, part, start, length);
+			up(&bdev->bd_sem);
+			return 0;
+		case BLKPG_DEL_PARTITION:
+			if (!disk->part[part-1])
+				return -ENXIO;
+			if (disk->part[part - 1]->nr_sects == 0)
+				return -ENXIO;
+			bdevp = bdget_disk(disk, part);
+			if (!bdevp)
+				return -ENOMEM;
+			down(&bdevp->bd_sem);
+			if (bdevp->bd_openers) {
+				up(&bdevp->bd_sem);
+				bdput(bdevp);
+				return -EBUSY;
+			}
+			/* all seems OK */
+			fsync_bdev(bdevp);
+			invalidate_bdev(bdevp, 0);
+
+			down(&bdev->bd_sem);
+			delete_partition(disk, part);
+			up(&bdev->bd_sem);
+			up(&bdevp->bd_sem);
+			bdput(bdevp);
+
+			return 0;
+		default:
+			return -EINVAL;
+	}
+}
+
+static int blkdev_reread_part(struct block_device *bdev)
+{
+	struct gendisk *disk = bdev->bd_disk;
+	int res;
+
+	if (disk->minors == 1 || bdev != bdev->bd_contains)
+		return -EINVAL;
+	if (!capable(CAP_SYS_ADMIN))
+		return -EACCES;
+	if (down_trylock(&bdev->bd_sem))
+		return -EBUSY;
+	res = rescan_partitions(disk, bdev);
+	up(&bdev->bd_sem);
+	return res;
+}
+
+static int put_ushort(unsigned long arg, unsigned short val)
+{
+	return put_user(val, (unsigned short __user *)arg);
+}
+
+static int put_int(unsigned long arg, int val)
+{
+	return put_user(val, (int __user *)arg);
+}
+
+static int put_long(unsigned long arg, long val)
+{
+	return put_user(val, (long __user *)arg);
+}
+
+static int put_ulong(unsigned long arg, unsigned long val)
+{
+	return put_user(val, (unsigned long __user *)arg);
+}
+
+static int put_u64(unsigned long arg, u64 val)
+{
+	return put_user(val, (u64 __user *)arg);
+}
+
+static int blkdev_locked_ioctl(struct file *file, struct block_device *bdev,
+				unsigned cmd, unsigned long arg)
+{
+	struct backing_dev_info *bdi;
+	int ret, n;
+
+	switch (cmd) {
+	case BLKRAGET:
+	case BLKFRAGET:
+		if (!arg)
+			return -EINVAL;
+		bdi = blk_get_backing_dev_info(bdev);
+		if (bdi == NULL)
+			return -ENOTTY;
+		return put_long(arg, (bdi->ra_pages * PAGE_CACHE_SIZE) / 512);
+	case BLKROGET:
+		return put_int(arg, bdev_read_only(bdev) != 0);
+	case BLKBSZGET: /* get the logical block size (cf. BLKSSZGET) */
+		return put_int(arg, block_size(bdev));
+	case BLKSSZGET: /* get block device hardware sector size */
+		return put_int(arg, bdev_hardsect_size(bdev));
+	case BLKSECTGET:
+		return put_ushort(arg, bdev_get_queue(bdev)->max_sectors);
+	case BLKRASET:
+	case BLKFRASET:
+		if(!capable(CAP_SYS_ADMIN))
+			return -EACCES;
+		bdi = blk_get_backing_dev_info(bdev);
+		if (bdi == NULL)
+			return -ENOTTY;
+		bdi->ra_pages = (arg * 512) / PAGE_CACHE_SIZE;
+		return 0;
+	case BLKBSZSET:
+		/* set the logical block size */
+		if (!capable(CAP_SYS_ADMIN))
+			return -EACCES;
+		if (!arg)
+			return -EINVAL;
+		if (get_user(n, (int __user *) arg))
+			return -EFAULT;
+		if (bd_claim(bdev, file) < 0)
+			return -EBUSY;
+		ret = set_blocksize(bdev, n);
+		bd_release(bdev);
+		return ret;
+	case BLKPG:
+		return blkpg_ioctl(bdev, (struct blkpg_ioctl_arg __user *) arg);
+	case BLKRRPART:
+		return blkdev_reread_part(bdev);
+	case BLKGETSIZE:
+		if ((bdev->bd_inode->i_size >> 9) > ~0UL)
+			return -EFBIG;
+		return put_ulong(arg, bdev->bd_inode->i_size >> 9);
+	case BLKGETSIZE64:
+		return put_u64(arg, bdev->bd_inode->i_size);
+	}
+	return -ENOIOCTLCMD;
+}
+
+static int blkdev_driver_ioctl(struct inode *inode, struct file *file,
+		struct gendisk *disk, unsigned cmd, unsigned long arg)
+{
+	int ret;
+	if (disk->fops->unlocked_ioctl)
+		return disk->fops->unlocked_ioctl(file, cmd, arg);
+
+	if (disk->fops->ioctl) {
+		lock_kernel();
+		ret = disk->fops->ioctl(inode, file, cmd, arg);
+		unlock_kernel();
+		return ret;
+	}
+
+	return -ENOTTY;
+}
+
+int blkdev_ioctl(struct inode *inode, struct file *file, unsigned cmd,
+			unsigned long arg)
+{
+	struct block_device *bdev = inode->i_bdev;
+	struct gendisk *disk = bdev->bd_disk;
+	int ret, n;
+
+	switch(cmd) {
+	case BLKFLSBUF:
+		if (!capable(CAP_SYS_ADMIN))
+			return -EACCES;
+
+		ret = blkdev_driver_ioctl(inode, file, disk, cmd, arg);
+		/* -EINVAL to handle old uncorrected drivers */
+		if (ret != -EINVAL && ret != -ENOTTY)
+			return ret;
+
+		lock_kernel();
+		fsync_bdev(bdev);
+		invalidate_bdev(bdev, 0);
+		unlock_kernel();
+		return 0;
+
+	case BLKROSET:
+		ret = blkdev_driver_ioctl(inode, file, disk, cmd, arg);
+		/* -EINVAL to handle old uncorrected drivers */
+		if (ret != -EINVAL && ret != -ENOTTY)
+			return ret;
+		if (!capable(CAP_SYS_ADMIN))
+			return -EACCES;
+		if (get_user(n, (int __user *)(arg)))
+			return -EFAULT;
+		lock_kernel();
+		set_device_ro(bdev, n);
+		unlock_kernel();
+		return 0;
+	}
+
+	lock_kernel();
+	ret = blkdev_locked_ioctl(file, bdev, cmd, arg);
+	unlock_kernel();
+	if (ret != -ENOIOCTLCMD)
+		return ret;
+
+	return blkdev_driver_ioctl(inode, file, disk, cmd, arg);
+}
+
+/* Most of the generic ioctls are handled in the normal fallback path.
+   This assumes the blkdev's low level compat_ioctl always returns
+   ENOIOCTLCMD for unknown ioctls. */
+long compat_blkdev_ioctl(struct file *file, unsigned cmd, unsigned long arg)
+{
+	struct block_device *bdev = file->f_dentry->d_inode->i_bdev;
+	struct gendisk *disk = bdev->bd_disk;
+	int ret = -ENOIOCTLCMD;
+	if (disk->fops->compat_ioctl) {
+		lock_kernel();
+		ret = disk->fops->compat_ioctl(file, cmd, arg);
+		unlock_kernel();
+	}
+	return ret;
+}
+
+EXPORT_SYMBOL_GPL(blkdev_ioctl);
diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c
new file mode 100644
index 00000000000..5f52e30b43f
--- /dev/null
+++ b/block/ll_rw_blk.c
@@ -0,0 +1,3612 @@
+/*
+ *  linux/drivers/block/ll_rw_blk.c
+ *
+ * Copyright (C) 1991, 1992 Linus Torvalds
+ * Copyright (C) 1994,      Karl Keyte: Added support for disk statistics
+ * Elevator latency, (C) 2000  Andrea Arcangeli <andrea@suse.de> SuSE
+ * Queue request tables / lock, selectable elevator, Jens Axboe <axboe@suse.de>
+ * kernel-doc documentation started by NeilBrown <neilb@cse.unsw.edu.au> -  July2000
+ * bio rewrite, highmem i/o, etc, Jens Axboe <axboe@suse.de> - may 2001
+ */
+
+/*
+ * This handles all read/write requests to block devices
+ */
+#include <linux/config.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/backing-dev.h>
+#include <linux/bio.h>
+#include <linux/blkdev.h>
+#include <linux/highmem.h>
+#include <linux/mm.h>
+#include <linux/kernel_stat.h>
+#include <linux/string.h>
+#include <linux/init.h>
+#include <linux/bootmem.h>	/* for max_pfn/max_low_pfn */
+#include <linux/completion.h>
+#include <linux/slab.h>
+#include <linux/swap.h>
+#include <linux/writeback.h>
+#include <linux/blkdev.h>
+
+/*
+ * for max sense size
+ */
+#include <scsi/scsi_cmnd.h>
+
+static void blk_unplug_work(void *data);
+static void blk_unplug_timeout(unsigned long data);
+static void drive_stat_acct(struct request *rq, int nr_sectors, int new_io);
+
+/*
+ * For the allocated request tables
+ */
+static kmem_cache_t *request_cachep;
+
+/*
+ * For queue allocation
+ */
+static kmem_cache_t *requestq_cachep;
+
+/*
+ * For io context allocations
+ */
+static kmem_cache_t *iocontext_cachep;
+
+static wait_queue_head_t congestion_wqh[2] = {
+		__WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
+		__WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
+	};
+
+/*
+ * Controlling structure to kblockd
+ */
+static struct workqueue_struct *kblockd_workqueue; 
+
+unsigned long blk_max_low_pfn, blk_max_pfn;
+
+EXPORT_SYMBOL(blk_max_low_pfn);
+EXPORT_SYMBOL(blk_max_pfn);
+
+/* Amount of time in which a process may batch requests */
+#define BLK_BATCH_TIME	(HZ/50UL)
+
+/* Number of requests a "batching" process may submit */
+#define BLK_BATCH_REQ	32
+
+/*
+ * Return the threshold (number of used requests) at which the queue is
+ * considered to be congested.  It include a little hysteresis to keep the
+ * context switch rate down.
+ */
+static inline int queue_congestion_on_threshold(struct request_queue *q)
+{
+	return q->nr_congestion_on;
+}
+
+/*
+ * The threshold at which a queue is considered to be uncongested
+ */
+static inline int queue_congestion_off_threshold(struct request_queue *q)
+{
+	return q->nr_congestion_off;
+}
+
+static void blk_queue_congestion_threshold(struct request_queue *q)
+{
+	int nr;
+
+	nr = q->nr_requests - (q->nr_requests / 8) + 1;
+	if (nr > q->nr_requests)
+		nr = q->nr_requests;
+	q->nr_congestion_on = nr;
+
+	nr = q->nr_requests - (q->nr_requests / 8) - (q->nr_requests / 16) - 1;
+	if (nr < 1)
+		nr = 1;
+	q->nr_congestion_off = nr;
+}
+
+/*
+ * A queue has just exitted congestion.  Note this in the global counter of
+ * congested queues, and wake up anyone who was waiting for requests to be
+ * put back.
+ */
+static void clear_queue_congested(request_queue_t *q, int rw)
+{
+	enum bdi_state bit;
+	wait_queue_head_t *wqh = &congestion_wqh[rw];
+
+	bit = (rw == WRITE) ? BDI_write_congested : BDI_read_congested;
+	clear_bit(bit, &q->backing_dev_info.state);
+	smp_mb__after_clear_bit();
+	if (waitqueue_active(wqh))
+		wake_up(wqh);
+}
+
+/*
+ * A queue has just entered congestion.  Flag that in the queue's VM-visible
+ * state flags and increment the global gounter of congested queues.
+ */
+static void set_queue_congested(request_queue_t *q, int rw)
+{
+	enum bdi_state bit;
+
+	bit = (rw == WRITE) ? BDI_write_congested : BDI_read_congested;
+	set_bit(bit, &q->backing_dev_info.state);
+}
+
+/**
+ * blk_get_backing_dev_info - get the address of a queue's backing_dev_info
+ * @bdev:	device
+ *
+ * Locates the passed device's request queue and returns the address of its
+ * backing_dev_info
+ *
+ * Will return NULL if the request queue cannot be located.
+ */
+struct backing_dev_info *blk_get_backing_dev_info(struct block_device *bdev)
+{
+	struct backing_dev_info *ret = NULL;
+	request_queue_t *q = bdev_get_queue(bdev);
+
+	if (q)
+		ret = &q->backing_dev_info;
+	return ret;
+}
+
+EXPORT_SYMBOL(blk_get_backing_dev_info);
+
+void blk_queue_activity_fn(request_queue_t *q, activity_fn *fn, void *data)
+{
+	q->activity_fn = fn;
+	q->activity_data = data;
+}
+
+EXPORT_SYMBOL(blk_queue_activity_fn);
+
+/**
+ * blk_queue_prep_rq - set a prepare_request function for queue
+ * @q:		queue
+ * @pfn:	prepare_request function
+ *
+ * It's possible for a queue to register a prepare_request callback which
+ * is invoked before the request is handed to the request_fn. The goal of
+ * the function is to prepare a request for I/O, it can be used to build a
+ * cdb from the request data for instance.
+ *
+ */
+void blk_queue_prep_rq(request_queue_t *q, prep_rq_fn *pfn)
+{
+	q->prep_rq_fn = pfn;
+}
+
+EXPORT_SYMBOL(blk_queue_prep_rq);
+
+/**
+ * blk_queue_merge_bvec - set a merge_bvec function for queue
+ * @q:		queue
+ * @mbfn:	merge_bvec_fn
+ *
+ * Usually queues have static limitations on the max sectors or segments that
+ * we can put in a request. Stacking drivers may have some settings that
+ * are dynamic, and thus we have to query the queue whether it is ok to
+ * add a new bio_vec to a bio at a given offset or not. If the block device
+ * has such limitations, it needs to register a merge_bvec_fn to control
+ * the size of bio's sent to it. Note that a block device *must* allow a
+ * single page to be added to an empty bio. The block device driver may want
+ * to use the bio_split() function to deal with these bio's. By default
+ * no merge_bvec_fn is defined for a queue, and only the fixed limits are
+ * honored.
+ */
+void blk_queue_merge_bvec(request_queue_t *q, merge_bvec_fn *mbfn)
+{
+	q->merge_bvec_fn = mbfn;
+}
+
+EXPORT_SYMBOL(blk_queue_merge_bvec);
+
+/**
+ * blk_queue_make_request - define an alternate make_request function for a device
+ * @q:  the request queue for the device to be affected
+ * @mfn: the alternate make_request function
+ *
+ * Description:
+ *    The normal way for &struct bios to be passed to a device
+ *    driver is for them to be collected into requests on a request
+ *    queue, and then to allow the device driver to select requests
+ *    off that queue when it is ready.  This works well for many block
+ *    devices. However some block devices (typically virtual devices
+ *    such as md or lvm) do not benefit from the processing on the
+ *    request queue, and are served best by having the requests passed
+ *    directly to them.  This can be achieved by providing a function
+ *    to blk_queue_make_request().
+ *
+ * Caveat:
+ *    The driver that does this *must* be able to deal appropriately
+ *    with buffers in "highmemory". This can be accomplished by either calling
+ *    __bio_kmap_atomic() to get a temporary kernel mapping, or by calling
+ *    blk_queue_bounce() to create a buffer in normal memory.
+ **/
+void blk_queue_make_request(request_queue_t * q, make_request_fn * mfn)
+{
+	/*
+	 * set defaults
+	 */
+	q->nr_requests = BLKDEV_MAX_RQ;
+	blk_queue_max_phys_segments(q, MAX_PHYS_SEGMENTS);
+	blk_queue_max_hw_segments(q, MAX_HW_SEGMENTS);
+	q->make_request_fn = mfn;
+	q->backing_dev_info.ra_pages = (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE;
+	q->backing_dev_info.state = 0;
+	q->backing_dev_info.capabilities = BDI_CAP_MAP_COPY;
+	blk_queue_max_sectors(q, MAX_SECTORS);
+	blk_queue_hardsect_size(q, 512);
+	blk_queue_dma_alignment(q, 511);
+	blk_queue_congestion_threshold(q);
+	q->nr_batching = BLK_BATCH_REQ;
+
+	q->unplug_thresh = 4;		/* hmm */
+	q->unplug_delay = (3 * HZ) / 1000;	/* 3 milliseconds */
+	if (q->unplug_delay == 0)
+		q->unplug_delay = 1;
+
+	INIT_WORK(&q->unplug_work, blk_unplug_work, q);
+
+	q->unplug_timer.function = blk_unplug_timeout;
+	q->unplug_timer.data = (unsigned long)q;
+
+	/*
+	 * by default assume old behaviour and bounce for any highmem page
+	 */
+	blk_queue_bounce_limit(q, BLK_BOUNCE_HIGH);
+
+	blk_queue_activity_fn(q, NULL, NULL);
+}
+
+EXPORT_SYMBOL(blk_queue_make_request);
+
+static inline void rq_init(request_queue_t *q, struct request *rq)
+{
+	INIT_LIST_HEAD(&rq->queuelist);
+
+	rq->errors = 0;
+	rq->rq_status = RQ_ACTIVE;
+	rq->bio = rq->biotail = NULL;
+	rq->ioprio = 0;
+	rq->buffer = NULL;
+	rq->ref_count = 1;
+	rq->q = q;
+	rq->waiting = NULL;
+	rq->special = NULL;
+	rq->data_len = 0;
+	rq->data = NULL;
+	rq->nr_phys_segments = 0;
+	rq->sense = NULL;
+	rq->end_io = NULL;
+	rq->end_io_data = NULL;
+}
+
+/**
+ * blk_queue_ordered - does this queue support ordered writes
+ * @q:     the request queue
+ * @flag:  see below
+ *
+ * Description:
+ *   For journalled file systems, doing ordered writes on a commit
+ *   block instead of explicitly doing wait_on_buffer (which is bad
+ *   for performance) can be a big win. Block drivers supporting this
+ *   feature should call this function and indicate so.
+ *
+ **/
+void blk_queue_ordered(request_queue_t *q, int flag)
+{
+	switch (flag) {
+		case QUEUE_ORDERED_NONE:
+			if (q->flush_rq)
+				kmem_cache_free(request_cachep, q->flush_rq);
+			q->flush_rq = NULL;
+			q->ordered = flag;
+			break;
+		case QUEUE_ORDERED_TAG:
+			q->ordered = flag;
+			break;
+		case QUEUE_ORDERED_FLUSH:
+			q->ordered = flag;
+			if (!q->flush_rq)
+				q->flush_rq = kmem_cache_alloc(request_cachep,
+								GFP_KERNEL);
+			break;
+		default:
+			printk("blk_queue_ordered: bad value %d\n", flag);
+			break;
+	}
+}
+
+EXPORT_SYMBOL(blk_queue_ordered);
+
+/**
+ * blk_queue_issue_flush_fn - set function for issuing a flush
+ * @q:     the request queue
+ * @iff:   the function to be called issuing the flush
+ *
+ * Description:
+ *   If a driver supports issuing a flush command, the support is notified
+ *   to the block layer by defining it through this call.
+ *
+ **/
+void blk_queue_issue_flush_fn(request_queue_t *q, issue_flush_fn *iff)
+{
+	q->issue_flush_fn = iff;
+}
+
+EXPORT_SYMBOL(blk_queue_issue_flush_fn);
+
+/*
+ * Cache flushing for ordered writes handling
+ */
+static void blk_pre_flush_end_io(struct request *flush_rq)
+{
+	struct request *rq = flush_rq->end_io_data;
+	request_queue_t *q = rq->q;
+
+	elv_completed_request(q, flush_rq);
+
+	rq->flags |= REQ_BAR_PREFLUSH;
+
+	if (!flush_rq->errors)
+		elv_requeue_request(q, rq);
+	else {
+		q->end_flush_fn(q, flush_rq);
+		clear_bit(QUEUE_FLAG_FLUSH, &q->queue_flags);
+		q->request_fn(q);
+	}
+}
+
+static void blk_post_flush_end_io(struct request *flush_rq)
+{
+	struct request *rq = flush_rq->end_io_data;
+	request_queue_t *q = rq->q;
+
+	elv_completed_request(q, flush_rq);
+
+	rq->flags |= REQ_BAR_POSTFLUSH;
+
+	q->end_flush_fn(q, flush_rq);
+	clear_bit(QUEUE_FLAG_FLUSH, &q->queue_flags);
+	q->request_fn(q);
+}
+
+struct request *blk_start_pre_flush(request_queue_t *q, struct request *rq)
+{
+	struct request *flush_rq = q->flush_rq;
+
+	BUG_ON(!blk_barrier_rq(rq));
+
+	if (test_and_set_bit(QUEUE_FLAG_FLUSH, &q->queue_flags))
+		return NULL;
+
+	rq_init(q, flush_rq);
+	flush_rq->elevator_private = NULL;
+	flush_rq->flags = REQ_BAR_FLUSH;
+	flush_rq->rq_disk = rq->rq_disk;
+	flush_rq->rl = NULL;
+
+	/*
+	 * prepare_flush returns 0 if no flush is needed, just mark both
+	 * pre and post flush as done in that case
+	 */
+	if (!q->prepare_flush_fn(q, flush_rq)) {
+		rq->flags |= REQ_BAR_PREFLUSH | REQ_BAR_POSTFLUSH;
+		clear_bit(QUEUE_FLAG_FLUSH, &q->queue_flags);
+		return rq;
+	}
+
+	/*
+	 * some drivers dequeue requests right away, some only after io
+	 * completion. make sure the request is dequeued.
+	 */
+	if (!list_empty(&rq->queuelist))
+		blkdev_dequeue_request(rq);
+
+	flush_rq->end_io_data = rq;
+	flush_rq->end_io = blk_pre_flush_end_io;
+
+	__elv_add_request(q, flush_rq, ELEVATOR_INSERT_FRONT, 0);
+	return flush_rq;
+}
+
+static void blk_start_post_flush(request_queue_t *q, struct request *rq)
+{
+	struct request *flush_rq = q->flush_rq;
+
+	BUG_ON(!blk_barrier_rq(rq));
+
+	rq_init(q, flush_rq);
+	flush_rq->elevator_private = NULL;
+	flush_rq->flags = REQ_BAR_FLUSH;
+	flush_rq->rq_disk = rq->rq_disk;
+	flush_rq->rl = NULL;
+
+	if (q->prepare_flush_fn(q, flush_rq)) {
+		flush_rq->end_io_data = rq;
+		flush_rq->end_io = blk_post_flush_end_io;
+
+		__elv_add_request(q, flush_rq, ELEVATOR_INSERT_FRONT, 0);
+		q->request_fn(q);
+	}
+}
+
+static inline int blk_check_end_barrier(request_queue_t *q, struct request *rq,
+					int sectors)
+{
+	if (sectors > rq->nr_sectors)
+		sectors = rq->nr_sectors;
+
+	rq->nr_sectors -= sectors;
+	return rq->nr_sectors;
+}
+
+static int __blk_complete_barrier_rq(request_queue_t *q, struct request *rq,
+				     int sectors, int queue_locked)
+{
+	if (q->ordered != QUEUE_ORDERED_FLUSH)
+		return 0;
+	if (!blk_fs_request(rq) || !blk_barrier_rq(rq))
+		return 0;
+	if (blk_barrier_postflush(rq))
+		return 0;
+
+	if (!blk_check_end_barrier(q, rq, sectors)) {
+		unsigned long flags = 0;
+
+		if (!queue_locked)
+			spin_lock_irqsave(q->queue_lock, flags);
+
+		blk_start_post_flush(q, rq);
+
+		if (!queue_locked)
+			spin_unlock_irqrestore(q->queue_lock, flags);
+	}
+
+	return 1;
+}
+
+/**
+ * blk_complete_barrier_rq - complete possible barrier request
+ * @q:  the request queue for the device
+ * @rq:  the request
+ * @sectors:  number of sectors to complete
+ *
+ * Description:
+ *   Used in driver end_io handling to determine whether to postpone
+ *   completion of a barrier request until a post flush has been done. This
+ *   is the unlocked variant, used if the caller doesn't already hold the
+ *   queue lock.
+ **/
+int blk_complete_barrier_rq(request_queue_t *q, struct request *rq, int sectors)
+{
+	return __blk_complete_barrier_rq(q, rq, sectors, 0);
+}
+EXPORT_SYMBOL(blk_complete_barrier_rq);
+
+/**
+ * blk_complete_barrier_rq_locked - complete possible barrier request
+ * @q:  the request queue for the device
+ * @rq:  the request
+ * @sectors:  number of sectors to complete
+ *
+ * Description:
+ *   See blk_complete_barrier_rq(). This variant must be used if the caller
+ *   holds the queue lock.
+ **/
+int blk_complete_barrier_rq_locked(request_queue_t *q, struct request *rq,
+				   int sectors)
+{
+	return __blk_complete_barrier_rq(q, rq, sectors, 1);
+}
+EXPORT_SYMBOL(blk_complete_barrier_rq_locked);
+
+/**
+ * blk_queue_bounce_limit - set bounce buffer limit for queue
+ * @q:  the request queue for the device
+ * @dma_addr:   bus address limit
+ *
+ * Description:
+ *    Different hardware can have different requirements as to what pages
+ *    it can do I/O directly to. A low level driver can call
+ *    blk_queue_bounce_limit to have lower memory pages allocated as bounce
+ *    buffers for doing I/O to pages residing above @page. By default
+ *    the block layer sets this to the highest numbered "low" memory page.
+ **/
+void blk_queue_bounce_limit(request_queue_t *q, u64 dma_addr)
+{
+	unsigned long bounce_pfn = dma_addr >> PAGE_SHIFT;
+
+	/*
+	 * set appropriate bounce gfp mask -- unfortunately we don't have a
+	 * full 4GB zone, so we have to resort to low memory for any bounces.
+	 * ISA has its own < 16MB zone.
+	 */
+	if (bounce_pfn < blk_max_low_pfn) {
+		BUG_ON(dma_addr < BLK_BOUNCE_ISA);
+		init_emergency_isa_pool();
+		q->bounce_gfp = GFP_NOIO | GFP_DMA;
+	} else
+		q->bounce_gfp = GFP_NOIO;
+
+	q->bounce_pfn = bounce_pfn;
+}
+
+EXPORT_SYMBOL(blk_queue_bounce_limit);
+
+/**
+ * blk_queue_max_sectors - set max sectors for a request for this queue
+ * @q:  the request queue for the device
+ * @max_sectors:  max sectors in the usual 512b unit
+ *
+ * Description:
+ *    Enables a low level driver to set an upper limit on the size of
+ *    received requests.
+ **/
+void blk_queue_max_sectors(request_queue_t *q, unsigned short max_sectors)
+{
+	if ((max_sectors << 9) < PAGE_CACHE_SIZE) {
+		max_sectors = 1 << (PAGE_CACHE_SHIFT - 9);
+		printk("%s: set to minimum %d\n", __FUNCTION__, max_sectors);
+	}
+
+	q->max_sectors = q->max_hw_sectors = max_sectors;
+}
+
+EXPORT_SYMBOL(blk_queue_max_sectors);
+
+/**
+ * blk_queue_max_phys_segments - set max phys segments for a request for this queue
+ * @q:  the request queue for the device
+ * @max_segments:  max number of segments
+ *
+ * Description:
+ *    Enables a low level driver to set an upper limit on the number of
+ *    physical data segments in a request.  This would be the largest sized
+ *    scatter list the driver could handle.
+ **/
+void blk_queue_max_phys_segments(request_queue_t *q, unsigned short max_segments)
+{
+	if (!max_segments) {
+		max_segments = 1;
+		printk("%s: set to minimum %d\n", __FUNCTION__, max_segments);
+	}
+
+	q->max_phys_segments = max_segments;
+}
+
+EXPORT_SYMBOL(blk_queue_max_phys_segments);
+
+/**
+ * blk_queue_max_hw_segments - set max hw segments for a request for this queue
+ * @q:  the request queue for the device
+ * @max_segments:  max number of segments
+ *
+ * Description:
+ *    Enables a low level driver to set an upper limit on the number of
+ *    hw data segments in a request.  This would be the largest number of
+ *    address/length pairs the host adapter can actually give as once
+ *    to the device.
+ **/
+void blk_queue_max_hw_segments(request_queue_t *q, unsigned short max_segments)
+{
+	if (!max_segments) {
+		max_segments = 1;
+		printk("%s: set to minimum %d\n", __FUNCTION__, max_segments);
+	}
+
+	q->max_hw_segments = max_segments;
+}
+
+EXPORT_SYMBOL(blk_queue_max_hw_segments);
+
+/**
+ * blk_queue_max_segment_size - set max segment size for blk_rq_map_sg
+ * @q:  the request queue for the device
+ * @max_size:  max size of segment in bytes
+ *
+ * Description:
+ *    Enables a low level driver to set an upper limit on the size of a
+ *    coalesced segment
+ **/
+void blk_queue_max_segment_size(request_queue_t *q, unsigned int max_size)
+{
+	if (max_size < PAGE_CACHE_SIZE) {
+		max_size = PAGE_CACHE_SIZE;
+		printk("%s: set to minimum %d\n", __FUNCTION__, max_size);
+	}
+
+	q->max_segment_size = max_size;
+}
+
+EXPORT_SYMBOL(blk_queue_max_segment_size);
+
+/**
+ * blk_queue_hardsect_size - set hardware sector size for the queue
+ * @q:  the request queue for the device
+ * @size:  the hardware sector size, in bytes
+ *
+ * Description:
+ *   This should typically be set to the lowest possible sector size
+ *   that the hardware can operate on (possible without reverting to
+ *   even internal read-modify-write operations). Usually the default
+ *   of 512 covers most hardware.
+ **/
+void blk_queue_hardsect_size(request_queue_t *q, unsigned short size)
+{
+	q->hardsect_size = size;
+}
+
+EXPORT_SYMBOL(blk_queue_hardsect_size);
+
+/*
+ * Returns the minimum that is _not_ zero, unless both are zero.
+ */
+#define min_not_zero(l, r) (l == 0) ? r : ((r == 0) ? l : min(l, r))
+
+/**
+ * blk_queue_stack_limits - inherit underlying queue limits for stacked drivers
+ * @t:	the stacking driver (top)
+ * @b:  the underlying device (bottom)
+ **/
+void blk_queue_stack_limits(request_queue_t *t, request_queue_t *b)
+{
+	/* zero is "infinity" */
+	t->max_sectors = t->max_hw_sectors =
+		min_not_zero(t->max_sectors,b->max_sectors);
+
+	t->max_phys_segments = min(t->max_phys_segments,b->max_phys_segments);
+	t->max_hw_segments = min(t->max_hw_segments,b->max_hw_segments);
+	t->max_segment_size = min(t->max_segment_size,b->max_segment_size);
+	t->hardsect_size = max(t->hardsect_size,b->hardsect_size);
+}
+
+EXPORT_SYMBOL(blk_queue_stack_limits);
+
+/**
+ * blk_queue_segment_boundary - set boundary rules for segment merging
+ * @q:  the request queue for the device
+ * @mask:  the memory boundary mask
+ **/
+void blk_queue_segment_boundary(request_queue_t *q, unsigned long mask)
+{
+	if (mask < PAGE_CACHE_SIZE - 1) {
+		mask = PAGE_CACHE_SIZE - 1;
+		printk("%s: set to minimum %lx\n", __FUNCTION__, mask);
+	}
+
+	q->seg_boundary_mask = mask;
+}
+
+EXPORT_SYMBOL(blk_queue_segment_boundary);
+
+/**
+ * blk_queue_dma_alignment - set dma length and memory alignment
+ * @q:     the request queue for the device
+ * @mask:  alignment mask
+ *
+ * description:
+ *    set required memory and length aligment for direct dma transactions.
+ *    this is used when buiding direct io requests for the queue.
+ *
+ **/
+void blk_queue_dma_alignment(request_queue_t *q, int mask)
+{
+	q->dma_alignment = mask;
+}
+
+EXPORT_SYMBOL(blk_queue_dma_alignment);
+
+/**
+ * blk_queue_find_tag - find a request by its tag and queue
+ * @q:	 The request queue for the device
+ * @tag: The tag of the request
+ *
+ * Notes:
+ *    Should be used when a device returns a tag and you want to match
+ *    it with a request.
+ *
+ *    no locks need be held.
+ **/
+struct request *blk_queue_find_tag(request_queue_t *q, int tag)
+{
+	struct blk_queue_tag *bqt = q->queue_tags;
+
+	if (unlikely(bqt == NULL || tag >= bqt->real_max_depth))
+		return NULL;
+
+	return bqt->tag_index[tag];
+}
+
+EXPORT_SYMBOL(blk_queue_find_tag);
+
+/**
+ * __blk_queue_free_tags - release tag maintenance info
+ * @q:  the request queue for the device
+ *
+ *  Notes:
+ *    blk_cleanup_queue() will take care of calling this function, if tagging
+ *    has been used. So there's no need to call this directly.
+ **/
+static void __blk_queue_free_tags(request_queue_t *q)
+{
+	struct blk_queue_tag *bqt = q->queue_tags;
+
+	if (!bqt)
+		return;
+
+	if (atomic_dec_and_test(&bqt->refcnt)) {
+		BUG_ON(bqt->busy);
+		BUG_ON(!list_empty(&bqt->busy_list));
+
+		kfree(bqt->tag_index);
+		bqt->tag_index = NULL;
+
+		kfree(bqt->tag_map);
+		bqt->tag_map = NULL;
+
+		kfree(bqt);
+	}
+
+	q->queue_tags = NULL;
+	q->queue_flags &= ~(1 << QUEUE_FLAG_QUEUED);
+}
+
+/**
+ * blk_queue_free_tags - release tag maintenance info
+ * @q:  the request queue for the device
+ *
+ *  Notes:
+ *	This is used to disabled tagged queuing to a device, yet leave
+ *	queue in function.
+ **/
+void blk_queue_free_tags(request_queue_t *q)
+{
+	clear_bit(QUEUE_FLAG_QUEUED, &q->queue_flags);
+}
+
+EXPORT_SYMBOL(blk_queue_free_tags);
+
+static int
+init_tag_map(request_queue_t *q, struct blk_queue_tag *tags, int depth)
+{
+	struct request **tag_index;
+	unsigned long *tag_map;
+	int nr_ulongs;
+
+	if (depth > q->nr_requests * 2) {
+		depth = q->nr_requests * 2;
+		printk(KERN_ERR "%s: adjusted depth to %d\n",
+				__FUNCTION__, depth);
+	}
+
+	tag_index = kmalloc(depth * sizeof(struct request *), GFP_ATOMIC);
+	if (!tag_index)
+		goto fail;
+
+	nr_ulongs = ALIGN(depth, BITS_PER_LONG) / BITS_PER_LONG;
+	tag_map = kmalloc(nr_ulongs * sizeof(unsigned long), GFP_ATOMIC);
+	if (!tag_map)
+		goto fail;
+
+	memset(tag_index, 0, depth * sizeof(struct request *));
+	memset(tag_map, 0, nr_ulongs * sizeof(unsigned long));
+	tags->real_max_depth = depth;
+	tags->max_depth = depth;
+	tags->tag_index = tag_index;
+	tags->tag_map = tag_map;
+
+	return 0;
+fail:
+	kfree(tag_index);
+	return -ENOMEM;
+}
+
+/**
+ * blk_queue_init_tags - initialize the queue tag info
+ * @q:  the request queue for the device
+ * @depth:  the maximum queue depth supported
+ * @tags: the tag to use
+ **/
+int blk_queue_init_tags(request_queue_t *q, int depth,
+			struct blk_queue_tag *tags)
+{
+	int rc;
+
+	BUG_ON(tags && q->queue_tags && tags != q->queue_tags);
+
+	if (!tags && !q->queue_tags) {
+		tags = kmalloc(sizeof(struct blk_queue_tag), GFP_ATOMIC);
+		if (!tags)
+			goto fail;
+
+		if (init_tag_map(q, tags, depth))
+			goto fail;
+
+		INIT_LIST_HEAD(&tags->busy_list);
+		tags->busy = 0;
+		atomic_set(&tags->refcnt, 1);
+	} else if (q->queue_tags) {
+		if ((rc = blk_queue_resize_tags(q, depth)))
+			return rc;
+		set_bit(QUEUE_FLAG_QUEUED, &q->queue_flags);
+		return 0;
+	} else
+		atomic_inc(&tags->refcnt);
+
+	/*
+	 * assign it, all done
+	 */
+	q->queue_tags = tags;
+	q->queue_flags |= (1 << QUEUE_FLAG_QUEUED);
+	return 0;
+fail:
+	kfree(tags);
+	return -ENOMEM;
+}
+
+EXPORT_SYMBOL(blk_queue_init_tags);
+
+/**
+ * blk_queue_resize_tags - change the queueing depth
+ * @q:  the request queue for the device
+ * @new_depth: the new max command queueing depth
+ *
+ *  Notes:
+ *    Must be called with the queue lock held.
+ **/
+int blk_queue_resize_tags(request_queue_t *q, int new_depth)
+{
+	struct blk_queue_tag *bqt = q->queue_tags;
+	struct request **tag_index;
+	unsigned long *tag_map;
+	int max_depth, nr_ulongs;
+
+	if (!bqt)
+		return -ENXIO;
+
+	/*
+	 * if we already have large enough real_max_depth.  just
+	 * adjust max_depth.  *NOTE* as requests with tag value
+	 * between new_depth and real_max_depth can be in-flight, tag
+	 * map can not be shrunk blindly here.
+	 */
+	if (new_depth <= bqt->real_max_depth) {
+		bqt->max_depth = new_depth;
+		return 0;
+	}
+
+	/*
+	 * save the old state info, so we can copy it back
+	 */
+	tag_index = bqt->tag_index;
+	tag_map = bqt->tag_map;
+	max_depth = bqt->real_max_depth;
+
+	if (init_tag_map(q, bqt, new_depth))
+		return -ENOMEM;
+
+	memcpy(bqt->tag_index, tag_index, max_depth * sizeof(struct request *));
+	nr_ulongs = ALIGN(max_depth, BITS_PER_LONG) / BITS_PER_LONG;
+	memcpy(bqt->tag_map, tag_map, nr_ulongs * sizeof(unsigned long));
+
+	kfree(tag_index);
+	kfree(tag_map);
+	return 0;
+}
+
+EXPORT_SYMBOL(blk_queue_resize_tags);
+
+/**
+ * blk_queue_end_tag - end tag operations for a request
+ * @q:  the request queue for the device
+ * @rq: the request that has completed
+ *
+ *  Description:
+ *    Typically called when end_that_request_first() returns 0, meaning
+ *    all transfers have been done for a request. It's important to call
+ *    this function before end_that_request_last(), as that will put the
+ *    request back on the free list thus corrupting the internal tag list.
+ *
+ *  Notes:
+ *   queue lock must be held.
+ **/
+void blk_queue_end_tag(request_queue_t *q, struct request *rq)
+{
+	struct blk_queue_tag *bqt = q->queue_tags;
+	int tag = rq->tag;
+
+	BUG_ON(tag == -1);
+
+	if (unlikely(tag >= bqt->real_max_depth))
+		/*
+		 * This can happen after tag depth has been reduced.
+		 * FIXME: how about a warning or info message here?
+		 */
+		return;
+
+	if (unlikely(!__test_and_clear_bit(tag, bqt->tag_map))) {
+		printk(KERN_ERR "%s: attempt to clear non-busy tag (%d)\n",
+		       __FUNCTION__, tag);
+		return;
+	}
+
+	list_del_init(&rq->queuelist);
+	rq->flags &= ~REQ_QUEUED;
+	rq->tag = -1;
+
+	if (unlikely(bqt->tag_index[tag] == NULL))
+		printk(KERN_ERR "%s: tag %d is missing\n",
+		       __FUNCTION__, tag);
+
+	bqt->tag_index[tag] = NULL;
+	bqt->busy--;
+}
+
+EXPORT_SYMBOL(blk_queue_end_tag);
+
+/**
+ * blk_queue_start_tag - find a free tag and assign it
+ * @q:  the request queue for the device
+ * @rq:  the block request that needs tagging
+ *
+ *  Description:
+ *    This can either be used as a stand-alone helper, or possibly be
+ *    assigned as the queue &prep_rq_fn (in which case &struct request
+ *    automagically gets a tag assigned). Note that this function
+ *    assumes that any type of request can be queued! if this is not
+ *    true for your device, you must check the request type before
+ *    calling this function.  The request will also be removed from
+ *    the request queue, so it's the drivers responsibility to readd
+ *    it if it should need to be restarted for some reason.
+ *
+ *  Notes:
+ *   queue lock must be held.
+ **/
+int blk_queue_start_tag(request_queue_t *q, struct request *rq)
+{
+	struct blk_queue_tag *bqt = q->queue_tags;
+	int tag;
+
+	if (unlikely((rq->flags & REQ_QUEUED))) {
+		printk(KERN_ERR 
+		       "%s: request %p for device [%s] already tagged %d",
+		       __FUNCTION__, rq,
+		       rq->rq_disk ? rq->rq_disk->disk_name : "?", rq->tag);
+		BUG();
+	}
+
+	tag = find_first_zero_bit(bqt->tag_map, bqt->max_depth);
+	if (tag >= bqt->max_depth)
+		return 1;
+
+	__set_bit(tag, bqt->tag_map);
+
+	rq->flags |= REQ_QUEUED;
+	rq->tag = tag;
+	bqt->tag_index[tag] = rq;
+	blkdev_dequeue_request(rq);
+	list_add(&rq->queuelist, &bqt->busy_list);
+	bqt->busy++;
+	return 0;
+}
+
+EXPORT_SYMBOL(blk_queue_start_tag);
+
+/**
+ * blk_queue_invalidate_tags - invalidate all pending tags
+ * @q:  the request queue for the device
+ *
+ *  Description:
+ *   Hardware conditions may dictate a need to stop all pending requests.
+ *   In this case, we will safely clear the block side of the tag queue and
+ *   readd all requests to the request queue in the right order.
+ *
+ *  Notes:
+ *   queue lock must be held.
+ **/
+void blk_queue_invalidate_tags(request_queue_t *q)
+{
+	struct blk_queue_tag *bqt = q->queue_tags;
+	struct list_head *tmp, *n;
+	struct request *rq;
+
+	list_for_each_safe(tmp, n, &bqt->busy_list) {
+		rq = list_entry_rq(tmp);
+
+		if (rq->tag == -1) {
+			printk(KERN_ERR
+			       "%s: bad tag found on list\n", __FUNCTION__);
+			list_del_init(&rq->queuelist);
+			rq->flags &= ~REQ_QUEUED;
+		} else
+			blk_queue_end_tag(q, rq);
+
+		rq->flags &= ~REQ_STARTED;
+		__elv_add_request(q, rq, ELEVATOR_INSERT_BACK, 0);
+	}
+}
+
+EXPORT_SYMBOL(blk_queue_invalidate_tags);
+
+static char *rq_flags[] = {
+	"REQ_RW",
+	"REQ_FAILFAST",
+	"REQ_SORTED",
+	"REQ_SOFTBARRIER",
+	"REQ_HARDBARRIER",
+	"REQ_CMD",
+	"REQ_NOMERGE",
+	"REQ_STARTED",
+	"REQ_DONTPREP",
+	"REQ_QUEUED",
+	"REQ_ELVPRIV",
+	"REQ_PC",
+	"REQ_BLOCK_PC",
+	"REQ_SENSE",
+	"REQ_FAILED",
+	"REQ_QUIET",
+	"REQ_SPECIAL",
+	"REQ_DRIVE_CMD",
+	"REQ_DRIVE_TASK",
+	"REQ_DRIVE_TASKFILE",
+	"REQ_PREEMPT",
+	"REQ_PM_SUSPEND",
+	"REQ_PM_RESUME",
+	"REQ_PM_SHUTDOWN",
+};
+
+void blk_dump_rq_flags(struct request *rq, char *msg)
+{
+	int bit;
+
+	printk("%s: dev %s: flags = ", msg,
+		rq->rq_disk ? rq->rq_disk->disk_name : "?");
+	bit = 0;
+	do {
+		if (rq->flags & (1 << bit))
+			printk("%s ", rq_flags[bit]);
+		bit++;
+	} while (bit < __REQ_NR_BITS);
+
+	printk("\nsector %llu, nr/cnr %lu/%u\n", (unsigned long long)rq->sector,
+						       rq->nr_sectors,
+						       rq->current_nr_sectors);
+	printk("bio %p, biotail %p, buffer %p, data %p, len %u\n", rq->bio, rq->biotail, rq->buffer, rq->data, rq->data_len);
+
+	if (rq->flags & (REQ_BLOCK_PC | REQ_PC)) {
+		printk("cdb: ");
+		for (bit = 0; bit < sizeof(rq->cmd); bit++)
+			printk("%02x ", rq->cmd[bit]);
+		printk("\n");
+	}
+}
+
+EXPORT_SYMBOL(blk_dump_rq_flags);
+
+void blk_recount_segments(request_queue_t *q, struct bio *bio)
+{
+	struct bio_vec *bv, *bvprv = NULL;
+	int i, nr_phys_segs, nr_hw_segs, seg_size, hw_seg_size, cluster;
+	int high, highprv = 1;
+
+	if (unlikely(!bio->bi_io_vec))
+		return;
+
+	cluster = q->queue_flags & (1 << QUEUE_FLAG_CLUSTER);
+	hw_seg_size = seg_size = nr_phys_segs = nr_hw_segs = 0;
+	bio_for_each_segment(bv, bio, i) {
+		/*
+		 * the trick here is making sure that a high page is never
+		 * considered part of another segment, since that might
+		 * change with the bounce page.
+		 */
+		high = page_to_pfn(bv->bv_page) >= q->bounce_pfn;
+		if (high || highprv)
+			goto new_hw_segment;
+		if (cluster) {
+			if (seg_size + bv->bv_len > q->max_segment_size)
+				goto new_segment;
+			if (!BIOVEC_PHYS_MERGEABLE(bvprv, bv))
+				goto new_segment;
+			if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bv))
+				goto new_segment;
+			if (BIOVEC_VIRT_OVERSIZE(hw_seg_size + bv->bv_len))
+				goto new_hw_segment;
+
+			seg_size += bv->bv_len;
+			hw_seg_size += bv->bv_len;
+			bvprv = bv;
+			continue;
+		}
+new_segment:
+		if (BIOVEC_VIRT_MERGEABLE(bvprv, bv) &&
+		    !BIOVEC_VIRT_OVERSIZE(hw_seg_size + bv->bv_len)) {
+			hw_seg_size += bv->bv_len;
+		} else {
+new_hw_segment:
+			if (hw_seg_size > bio->bi_hw_front_size)
+				bio->bi_hw_front_size = hw_seg_size;
+			hw_seg_size = BIOVEC_VIRT_START_SIZE(bv) + bv->bv_len;
+			nr_hw_segs++;
+		}
+
+		nr_phys_segs++;
+		bvprv = bv;
+		seg_size = bv->bv_len;
+		highprv = high;
+	}
+	if (hw_seg_size > bio->bi_hw_back_size)
+		bio->bi_hw_back_size = hw_seg_size;
+	if (nr_hw_segs == 1 && hw_seg_size > bio->bi_hw_front_size)
+		bio->bi_hw_front_size = hw_seg_size;
+	bio->bi_phys_segments = nr_phys_segs;
+	bio->bi_hw_segments = nr_hw_segs;
+	bio->bi_flags |= (1 << BIO_SEG_VALID);
+}
+
+
+static int blk_phys_contig_segment(request_queue_t *q, struct bio *bio,
+				   struct bio *nxt)
+{
+	if (!(q->queue_flags & (1 << QUEUE_FLAG_CLUSTER)))
+		return 0;
+
+	if (!BIOVEC_PHYS_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)))
+		return 0;
+	if (bio->bi_size + nxt->bi_size > q->max_segment_size)
+		return 0;
+
+	/*
+	 * bio and nxt are contigous in memory, check if the queue allows
+	 * these two to be merged into one
+	 */
+	if (BIO_SEG_BOUNDARY(q, bio, nxt))
+		return 1;
+
+	return 0;
+}
+
+static int blk_hw_contig_segment(request_queue_t *q, struct bio *bio,
+				 struct bio *nxt)
+{
+	if (unlikely(!bio_flagged(bio, BIO_SEG_VALID)))
+		blk_recount_segments(q, bio);
+	if (unlikely(!bio_flagged(nxt, BIO_SEG_VALID)))
+		blk_recount_segments(q, nxt);
+	if (!BIOVEC_VIRT_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)) ||
+	    BIOVEC_VIRT_OVERSIZE(bio->bi_hw_front_size + bio->bi_hw_back_size))
+		return 0;
+	if (bio->bi_size + nxt->bi_size > q->max_segment_size)
+		return 0;
+
+	return 1;
+}
+
+/*
+ * map a request to scatterlist, return number of sg entries setup. Caller
+ * must make sure sg can hold rq->nr_phys_segments entries
+ */
+int blk_rq_map_sg(request_queue_t *q, struct request *rq, struct scatterlist *sg)
+{
+	struct bio_vec *bvec, *bvprv;
+	struct bio *bio;
+	int nsegs, i, cluster;
+
+	nsegs = 0;
+	cluster = q->queue_flags & (1 << QUEUE_FLAG_CLUSTER);
+
+	/*
+	 * for each bio in rq
+	 */
+	bvprv = NULL;
+	rq_for_each_bio(bio, rq) {
+		/*
+		 * for each segment in bio
+		 */
+		bio_for_each_segment(bvec, bio, i) {
+			int nbytes = bvec->bv_len;
+
+			if (bvprv && cluster) {
+				if (sg[nsegs - 1].length + nbytes > q->max_segment_size)
+					goto new_segment;
+
+				if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec))
+					goto new_segment;
+				if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec))
+					goto new_segment;
+
+				sg[nsegs - 1].length += nbytes;
+			} else {
+new_segment:
+				memset(&sg[nsegs],0,sizeof(struct scatterlist));
+				sg[nsegs].page = bvec->bv_page;
+				sg[nsegs].length = nbytes;
+				sg[nsegs].offset = bvec->bv_offset;
+
+				nsegs++;
+			}
+			bvprv = bvec;
+		} /* segments in bio */
+	} /* bios in rq */
+
+	return nsegs;
+}
+
+EXPORT_SYMBOL(blk_rq_map_sg);
+
+/*
+ * the standard queue merge functions, can be overridden with device
+ * specific ones if so desired
+ */
+
+static inline int ll_new_mergeable(request_queue_t *q,
+				   struct request *req,
+				   struct bio *bio)
+{
+	int nr_phys_segs = bio_phys_segments(q, bio);
+
+	if (req->nr_phys_segments + nr_phys_segs > q->max_phys_segments) {
+		req->flags |= REQ_NOMERGE;
+		if (req == q->last_merge)
+			q->last_merge = NULL;
+		return 0;
+	}
+
+	/*
+	 * A hw segment is just getting larger, bump just the phys
+	 * counter.
+	 */
+	req->nr_phys_segments += nr_phys_segs;
+	return 1;
+}
+
+static inline int ll_new_hw_segment(request_queue_t *q,
+				    struct request *req,
+				    struct bio *bio)
+{
+	int nr_hw_segs = bio_hw_segments(q, bio);
+	int nr_phys_segs = bio_phys_segments(q, bio);
+
+	if (req->nr_hw_segments + nr_hw_segs > q->max_hw_segments
+	    || req->nr_phys_segments + nr_phys_segs > q->max_phys_segments) {
+		req->flags |= REQ_NOMERGE;
+		if (req == q->last_merge)
+			q->last_merge = NULL;
+		return 0;
+	}
+
+	/*
+	 * This will form the start of a new hw segment.  Bump both
+	 * counters.
+	 */
+	req->nr_hw_segments += nr_hw_segs;
+	req->nr_phys_segments += nr_phys_segs;
+	return 1;
+}
+
+static int ll_back_merge_fn(request_queue_t *q, struct request *req, 
+			    struct bio *bio)
+{
+	int len;
+
+	if (req->nr_sectors + bio_sectors(bio) > q->max_sectors) {
+		req->flags |= REQ_NOMERGE;
+		if (req == q->last_merge)
+			q->last_merge = NULL;
+		return 0;
+	}
+	if (unlikely(!bio_flagged(req->biotail, BIO_SEG_VALID)))
+		blk_recount_segments(q, req->biotail);
+	if (unlikely(!bio_flagged(bio, BIO_SEG_VALID)))
+		blk_recount_segments(q, bio);
+	len = req->biotail->bi_hw_back_size + bio->bi_hw_front_size;
+	if (BIOVEC_VIRT_MERGEABLE(__BVEC_END(req->biotail), __BVEC_START(bio)) &&
+	    !BIOVEC_VIRT_OVERSIZE(len)) {
+		int mergeable =  ll_new_mergeable(q, req, bio);
+
+		if (mergeable) {
+			if (req->nr_hw_segments == 1)
+				req->bio->bi_hw_front_size = len;
+			if (bio->bi_hw_segments == 1)
+				bio->bi_hw_back_size = len;
+		}
+		return mergeable;
+	}
+
+	return ll_new_hw_segment(q, req, bio);
+}
+
+static int ll_front_merge_fn(request_queue_t *q, struct request *req, 
+			     struct bio *bio)
+{
+	int len;
+
+	if (req->nr_sectors + bio_sectors(bio) > q->max_sectors) {
+		req->flags |= REQ_NOMERGE;
+		if (req == q->last_merge)
+			q->last_merge = NULL;
+		return 0;
+	}
+	len = bio->bi_hw_back_size + req->bio->bi_hw_front_size;
+	if (unlikely(!bio_flagged(bio, BIO_SEG_VALID)))
+		blk_recount_segments(q, bio);
+	if (unlikely(!bio_flagged(req->bio, BIO_SEG_VALID)))
+		blk_recount_segments(q, req->bio);
+	if (BIOVEC_VIRT_MERGEABLE(__BVEC_END(bio), __BVEC_START(req->bio)) &&
+	    !BIOVEC_VIRT_OVERSIZE(len)) {
+		int mergeable =  ll_new_mergeable(q, req, bio);
+
+		if (mergeable) {
+			if (bio->bi_hw_segments == 1)
+				bio->bi_hw_front_size = len;
+			if (req->nr_hw_segments == 1)
+				req->biotail->bi_hw_back_size = len;
+		}
+		return mergeable;
+	}
+
+	return ll_new_hw_segment(q, req, bio);
+}
+
+static int ll_merge_requests_fn(request_queue_t *q, struct request *req,
+				struct request *next)
+{
+	int total_phys_segments;
+	int total_hw_segments;
+
+	/*
+	 * First check if the either of the requests are re-queued
+	 * requests.  Can't merge them if they are.
+	 */
+	if (req->special || next->special)
+		return 0;
+
+	/*
+	 * Will it become too large?
+	 */
+	if ((req->nr_sectors + next->nr_sectors) > q->max_sectors)
+		return 0;
+
+	total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
+	if (blk_phys_contig_segment(q, req->biotail, next->bio))
+		total_phys_segments--;
+
+	if (total_phys_segments > q->max_phys_segments)
+		return 0;
+
+	total_hw_segments = req->nr_hw_segments + next->nr_hw_segments;
+	if (blk_hw_contig_segment(q, req->biotail, next->bio)) {
+		int len = req->biotail->bi_hw_back_size + next->bio->bi_hw_front_size;
+		/*
+		 * propagate the combined length to the end of the requests
+		 */
+		if (req->nr_hw_segments == 1)
+			req->bio->bi_hw_front_size = len;
+		if (next->nr_hw_segments == 1)
+			next->biotail->bi_hw_back_size = len;
+		total_hw_segments--;
+	}
+
+	if (total_hw_segments > q->max_hw_segments)
+		return 0;
+
+	/* Merge is OK... */
+	req->nr_phys_segments = total_phys_segments;
+	req->nr_hw_segments = total_hw_segments;
+	return 1;
+}
+
+/*
+ * "plug" the device if there are no outstanding requests: this will
+ * force the transfer to start only after we have put all the requests
+ * on the list.
+ *
+ * This is called with interrupts off and no requests on the queue and
+ * with the queue lock held.
+ */
+void blk_plug_device(request_queue_t *q)
+{
+	WARN_ON(!irqs_disabled());
+
+	/*
+	 * don't plug a stopped queue, it must be paired with blk_start_queue()
+	 * which will restart the queueing
+	 */
+	if (test_bit(QUEUE_FLAG_STOPPED, &q->queue_flags))
+		return;
+
+	if (!test_and_set_bit(QUEUE_FLAG_PLUGGED, &q->queue_flags))
+		mod_timer(&q->unplug_timer, jiffies + q->unplug_delay);
+}
+
+EXPORT_SYMBOL(blk_plug_device);
+
+/*
+ * remove the queue from the plugged list, if present. called with
+ * queue lock held and interrupts disabled.
+ */
+int blk_remove_plug(request_queue_t *q)
+{
+	WARN_ON(!irqs_disabled());
+
+	if (!test_and_clear_bit(QUEUE_FLAG_PLUGGED, &q->queue_flags))
+		return 0;
+
+	del_timer(&q->unplug_timer);
+	return 1;
+}
+
+EXPORT_SYMBOL(blk_remove_plug);
+
+/*
+ * remove the plug and let it rip..
+ */
+void __generic_unplug_device(request_queue_t *q)
+{
+	if (unlikely(test_bit(QUEUE_FLAG_STOPPED, &q->queue_flags)))
+		return;
+
+	if (!blk_remove_plug(q))
+		return;
+
+	q->request_fn(q);
+}
+EXPORT_SYMBOL(__generic_unplug_device);
+
+/**
+ * generic_unplug_device - fire a request queue
+ * @q:    The &request_queue_t in question
+ *
+ * Description:
+ *   Linux uses plugging to build bigger requests queues before letting
+ *   the device have at them. If a queue is plugged, the I/O scheduler
+ *   is still adding and merging requests on the queue. Once the queue
+ *   gets unplugged, the request_fn defined for the queue is invoked and
+ *   transfers started.
+ **/
+void generic_unplug_device(request_queue_t *q)
+{
+	spin_lock_irq(q->queue_lock);
+	__generic_unplug_device(q);
+	spin_unlock_irq(q->queue_lock);
+}
+EXPORT_SYMBOL(generic_unplug_device);
+
+static void blk_backing_dev_unplug(struct backing_dev_info *bdi,
+				   struct page *page)
+{
+	request_queue_t *q = bdi->unplug_io_data;
+
+	/*
+	 * devices don't necessarily have an ->unplug_fn defined
+	 */
+	if (q->unplug_fn)
+		q->unplug_fn(q);
+}
+
+static void blk_unplug_work(void *data)
+{
+	request_queue_t *q = data;
+
+	q->unplug_fn(q);
+}
+
+static void blk_unplug_timeout(unsigned long data)
+{
+	request_queue_t *q = (request_queue_t *)data;
+
+	kblockd_schedule_work(&q->unplug_work);
+}
+
+/**
+ * blk_start_queue - restart a previously stopped queue
+ * @q:    The &request_queue_t in question
+ *
+ * Description:
+ *   blk_start_queue() will clear the stop flag on the queue, and call
+ *   the request_fn for the queue if it was in a stopped state when
+ *   entered. Also see blk_stop_queue(). Queue lock must be held.
+ **/
+void blk_start_queue(request_queue_t *q)
+{
+	clear_bit(QUEUE_FLAG_STOPPED, &q->queue_flags);
+
+	/*
+	 * one level of recursion is ok and is much faster than kicking
+	 * the unplug handling
+	 */
+	if (!test_and_set_bit(QUEUE_FLAG_REENTER, &q->queue_flags)) {
+		q->request_fn(q);
+		clear_bit(QUEUE_FLAG_REENTER, &q->queue_flags);
+	} else {
+		blk_plug_device(q);
+		kblockd_schedule_work(&q->unplug_work);
+	}
+}
+
+EXPORT_SYMBOL(blk_start_queue);
+
+/**
+ * blk_stop_queue - stop a queue
+ * @q:    The &request_queue_t in question
+ *
+ * Description:
+ *   The Linux block layer assumes that a block driver will consume all
+ *   entries on the request queue when the request_fn strategy is called.
+ *   Often this will not happen, because of hardware limitations (queue
+ *   depth settings). If a device driver gets a 'queue full' response,
+ *   or if it simply chooses not to queue more I/O at one point, it can
+ *   call this function to prevent the request_fn from being called until
+ *   the driver has signalled it's ready to go again. This happens by calling
+ *   blk_start_queue() to restart queue operations. Queue lock must be held.
+ **/
+void blk_stop_queue(request_queue_t *q)
+{
+	blk_remove_plug(q);
+	set_bit(QUEUE_FLAG_STOPPED, &q->queue_flags);
+}
+EXPORT_SYMBOL(blk_stop_queue);
+
+/**
+ * blk_sync_queue - cancel any pending callbacks on a queue
+ * @q: the queue
+ *
+ * Description:
+ *     The block layer may perform asynchronous callback activity
+ *     on a queue, such as calling the unplug function after a timeout.
+ *     A block device may call blk_sync_queue to ensure that any
+ *     such activity is cancelled, thus allowing it to release resources
+ *     the the callbacks might use. The caller must already have made sure
+ *     that its ->make_request_fn will not re-add plugging prior to calling
+ *     this function.
+ *
+ */
+void blk_sync_queue(struct request_queue *q)
+{
+	del_timer_sync(&q->unplug_timer);
+	kblockd_flush();
+}
+EXPORT_SYMBOL(blk_sync_queue);
+
+/**
+ * blk_run_queue - run a single device queue
+ * @q:	The queue to run
+ */
+void blk_run_queue(struct request_queue *q)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(q->queue_lock, flags);
+	blk_remove_plug(q);
+	if (!elv_queue_empty(q))
+		q->request_fn(q);
+	spin_unlock_irqrestore(q->queue_lock, flags);
+}
+EXPORT_SYMBOL(blk_run_queue);
+
+/**
+ * blk_cleanup_queue: - release a &request_queue_t when it is no longer needed
+ * @q:    the request queue to be released
+ *
+ * Description:
+ *     blk_cleanup_queue is the pair to blk_init_queue() or
+ *     blk_queue_make_request().  It should be called when a request queue is
+ *     being released; typically when a block device is being de-registered.
+ *     Currently, its primary task it to free all the &struct request
+ *     structures that were allocated to the queue and the queue itself.
+ *
+ * Caveat:
+ *     Hopefully the low level driver will have finished any
+ *     outstanding requests first...
+ **/
+void blk_cleanup_queue(request_queue_t * q)
+{
+	struct request_list *rl = &q->rq;
+
+	if (!atomic_dec_and_test(&q->refcnt))
+		return;
+
+	if (q->elevator)
+		elevator_exit(q->elevator);
+
+	blk_sync_queue(q);
+
+	if (rl->rq_pool)
+		mempool_destroy(rl->rq_pool);
+
+	if (q->queue_tags)
+		__blk_queue_free_tags(q);
+
+	blk_queue_ordered(q, QUEUE_ORDERED_NONE);
+
+	kmem_cache_free(requestq_cachep, q);
+}
+
+EXPORT_SYMBOL(blk_cleanup_queue);
+
+static int blk_init_free_list(request_queue_t *q)
+{
+	struct request_list *rl = &q->rq;
+
+	rl->count[READ] = rl->count[WRITE] = 0;
+	rl->starved[READ] = rl->starved[WRITE] = 0;
+	rl->elvpriv = 0;
+	init_waitqueue_head(&rl->wait[READ]);
+	init_waitqueue_head(&rl->wait[WRITE]);
+
+	rl->rq_pool = mempool_create_node(BLKDEV_MIN_RQ, mempool_alloc_slab,
+				mempool_free_slab, request_cachep, q->node);
+
+	if (!rl->rq_pool)
+		return -ENOMEM;
+
+	return 0;
+}
+
+static int __make_request(request_queue_t *, struct bio *);
+
+request_queue_t *blk_alloc_queue(gfp_t gfp_mask)
+{
+	return blk_alloc_queue_node(gfp_mask, -1);
+}
+EXPORT_SYMBOL(blk_alloc_queue);
+
+request_queue_t *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
+{
+	request_queue_t *q;
+
+	q = kmem_cache_alloc_node(requestq_cachep, gfp_mask, node_id);
+	if (!q)
+		return NULL;
+
+	memset(q, 0, sizeof(*q));
+	init_timer(&q->unplug_timer);
+	atomic_set(&q->refcnt, 1);
+
+	q->backing_dev_info.unplug_io_fn = blk_backing_dev_unplug;
+	q->backing_dev_info.unplug_io_data = q;
+
+	return q;
+}
+EXPORT_SYMBOL(blk_alloc_queue_node);
+
+/**
+ * blk_init_queue  - prepare a request queue for use with a block device
+ * @rfn:  The function to be called to process requests that have been
+ *        placed on the queue.
+ * @lock: Request queue spin lock
+ *
+ * Description:
+ *    If a block device wishes to use the standard request handling procedures,
+ *    which sorts requests and coalesces adjacent requests, then it must
+ *    call blk_init_queue().  The function @rfn will be called when there
+ *    are requests on the queue that need to be processed.  If the device
+ *    supports plugging, then @rfn may not be called immediately when requests
+ *    are available on the queue, but may be called at some time later instead.
+ *    Plugged queues are generally unplugged when a buffer belonging to one
+ *    of the requests on the queue is needed, or due to memory pressure.
+ *
+ *    @rfn is not required, or even expected, to remove all requests off the
+ *    queue, but only as many as it can handle at a time.  If it does leave
+ *    requests on the queue, it is responsible for arranging that the requests
+ *    get dealt with eventually.
+ *
+ *    The queue spin lock must be held while manipulating the requests on the
+ *    request queue.
+ *
+ *    Function returns a pointer to the initialized request queue, or NULL if
+ *    it didn't succeed.
+ *
+ * Note:
+ *    blk_init_queue() must be paired with a blk_cleanup_queue() call
+ *    when the block device is deactivated (such as at module unload).
+ **/
+
+request_queue_t *blk_init_queue(request_fn_proc *rfn, spinlock_t *lock)
+{
+	return blk_init_queue_node(rfn, lock, -1);
+}
+EXPORT_SYMBOL(blk_init_queue);
+
+request_queue_t *
+blk_init_queue_node(request_fn_proc *rfn, spinlock_t *lock, int node_id)
+{
+	request_queue_t *q = blk_alloc_queue_node(GFP_KERNEL, node_id);
+
+	if (!q)
+		return NULL;
+
+	q->node = node_id;
+	if (blk_init_free_list(q))
+		goto out_init;
+
+	/*
+	 * if caller didn't supply a lock, they get per-queue locking with
+	 * our embedded lock
+	 */
+	if (!lock) {
+		spin_lock_init(&q->__queue_lock);
+		lock = &q->__queue_lock;
+	}
+
+	q->request_fn		= rfn;
+	q->back_merge_fn       	= ll_back_merge_fn;
+	q->front_merge_fn      	= ll_front_merge_fn;
+	q->merge_requests_fn	= ll_merge_requests_fn;
+	q->prep_rq_fn		= NULL;
+	q->unplug_fn		= generic_unplug_device;
+	q->queue_flags		= (1 << QUEUE_FLAG_CLUSTER);
+	q->queue_lock		= lock;
+
+	blk_queue_segment_boundary(q, 0xffffffff);
+
+	blk_queue_make_request(q, __make_request);
+	blk_queue_max_segment_size(q, MAX_SEGMENT_SIZE);
+
+	blk_queue_max_hw_segments(q, MAX_HW_SEGMENTS);
+	blk_queue_max_phys_segments(q, MAX_PHYS_SEGMENTS);
+
+	/*
+	 * all done
+	 */
+	if (!elevator_init(q, NULL)) {
+		blk_queue_congestion_threshold(q);
+		return q;
+	}
+
+	blk_cleanup_queue(q);
+out_init:
+	kmem_cache_free(requestq_cachep, q);
+	return NULL;
+}
+EXPORT_SYMBOL(blk_init_queue_node);
+
+int blk_get_queue(request_queue_t *q)
+{
+	if (likely(!test_bit(QUEUE_FLAG_DEAD, &q->queue_flags))) {
+		atomic_inc(&q->refcnt);
+		return 0;
+	}
+
+	return 1;
+}
+
+EXPORT_SYMBOL(blk_get_queue);
+
+static inline void blk_free_request(request_queue_t *q, struct request *rq)
+{
+	if (rq->flags & REQ_ELVPRIV)
+		elv_put_request(q, rq);
+	mempool_free(rq, q->rq.rq_pool);
+}
+
+static inline struct request *
+blk_alloc_request(request_queue_t *q, int rw, struct bio *bio,
+		  int priv, gfp_t gfp_mask)
+{
+	struct request *rq = mempool_alloc(q->rq.rq_pool, gfp_mask);
+
+	if (!rq)
+		return NULL;
+
+	/*
+	 * first three bits are identical in rq->flags and bio->bi_rw,
+	 * see bio.h and blkdev.h
+	 */
+	rq->flags = rw;
+
+	if (priv) {
+		if (unlikely(elv_set_request(q, rq, bio, gfp_mask))) {
+			mempool_free(rq, q->rq.rq_pool);
+			return NULL;
+		}
+		rq->flags |= REQ_ELVPRIV;
+	}
+
+	return rq;
+}
+
+/*
+ * ioc_batching returns true if the ioc is a valid batching request and
+ * should be given priority access to a request.
+ */
+static inline int ioc_batching(request_queue_t *q, struct io_context *ioc)
+{
+	if (!ioc)
+		return 0;
+
+	/*
+	 * Make sure the process is able to allocate at least 1 request
+	 * even if the batch times out, otherwise we could theoretically
+	 * lose wakeups.
+	 */
+	return ioc->nr_batch_requests == q->nr_batching ||
+		(ioc->nr_batch_requests > 0
+		&& time_before(jiffies, ioc->last_waited + BLK_BATCH_TIME));
+}
+
+/*
+ * ioc_set_batching sets ioc to be a new "batcher" if it is not one. This
+ * will cause the process to be a "batcher" on all queues in the system. This
+ * is the behaviour we want though - once it gets a wakeup it should be given
+ * a nice run.
+ */
+static void ioc_set_batching(request_queue_t *q, struct io_context *ioc)
+{
+	if (!ioc || ioc_batching(q, ioc))
+		return;
+
+	ioc->nr_batch_requests = q->nr_batching;
+	ioc->last_waited = jiffies;
+}
+
+static void __freed_request(request_queue_t *q, int rw)
+{
+	struct request_list *rl = &q->rq;
+
+	if (rl->count[rw] < queue_congestion_off_threshold(q))
+		clear_queue_congested(q, rw);
+
+	if (rl->count[rw] + 1 <= q->nr_requests) {
+		if (waitqueue_active(&rl->wait[rw]))
+			wake_up(&rl->wait[rw]);
+
+		blk_clear_queue_full(q, rw);
+	}
+}
+
+/*
+ * A request has just been released.  Account for it, update the full and
+ * congestion status, wake up any waiters.   Called under q->queue_lock.
+ */
+static void freed_request(request_queue_t *q, int rw, int priv)
+{
+	struct request_list *rl = &q->rq;
+
+	rl->count[rw]--;
+	if (priv)
+		rl->elvpriv--;
+
+	__freed_request(q, rw);
+
+	if (unlikely(rl->starved[rw ^ 1]))
+		__freed_request(q, rw ^ 1);
+}
+
+#define blkdev_free_rq(list) list_entry((list)->next, struct request, queuelist)
+/*
+ * Get a free request, queue_lock must be held.
+ * Returns NULL on failure, with queue_lock held.
+ * Returns !NULL on success, with queue_lock *not held*.
+ */
+static struct request *get_request(request_queue_t *q, int rw, struct bio *bio,
+				   gfp_t gfp_mask)
+{
+	struct request *rq = NULL;
+	struct request_list *rl = &q->rq;
+	struct io_context *ioc = current_io_context(GFP_ATOMIC);
+	int priv;
+
+	if (rl->count[rw]+1 >= q->nr_requests) {
+		/*
+		 * The queue will fill after this allocation, so set it as
+		 * full, and mark this process as "batching". This process
+		 * will be allowed to complete a batch of requests, others
+		 * will be blocked.
+		 */
+		if (!blk_queue_full(q, rw)) {
+			ioc_set_batching(q, ioc);
+			blk_set_queue_full(q, rw);
+		}
+	}
+
+	switch (elv_may_queue(q, rw, bio)) {
+		case ELV_MQUEUE_NO:
+			goto rq_starved;
+		case ELV_MQUEUE_MAY:
+			break;
+		case ELV_MQUEUE_MUST:
+			goto get_rq;
+	}
+
+	if (blk_queue_full(q, rw) && !ioc_batching(q, ioc)) {
+		/*
+		 * The queue is full and the allocating process is not a
+		 * "batcher", and not exempted by the IO scheduler
+		 */
+		goto out;
+	}
+
+get_rq:
+	/*
+	 * Only allow batching queuers to allocate up to 50% over the defined
+	 * limit of requests, otherwise we could have thousands of requests
+	 * allocated with any setting of ->nr_requests
+	 */
+	if (rl->count[rw] >= (3 * q->nr_requests / 2))
+		goto out;
+
+	rl->count[rw]++;
+	rl->starved[rw] = 0;
+	if (rl->count[rw] >= queue_congestion_on_threshold(q))
+		set_queue_congested(q, rw);
+
+	priv = !test_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
+	if (priv)
+		rl->elvpriv++;
+
+	spin_unlock_irq(q->queue_lock);
+
+	rq = blk_alloc_request(q, rw, bio, priv, gfp_mask);
+	if (!rq) {
+		/*
+		 * Allocation failed presumably due to memory. Undo anything
+		 * we might have messed up.
+		 *
+		 * Allocating task should really be put onto the front of the
+		 * wait queue, but this is pretty rare.
+		 */
+		spin_lock_irq(q->queue_lock);
+		freed_request(q, rw, priv);
+
+		/*
+		 * in the very unlikely event that allocation failed and no
+		 * requests for this direction was pending, mark us starved
+		 * so that freeing of a request in the other direction will
+		 * notice us. another possible fix would be to split the
+		 * rq mempool into READ and WRITE
+		 */
+rq_starved:
+		if (unlikely(rl->count[rw] == 0))
+			rl->starved[rw] = 1;
+
+		goto out;
+	}
+
+	if (ioc_batching(q, ioc))
+		ioc->nr_batch_requests--;
+	
+	rq_init(q, rq);
+	rq->rl = rl;
+out:
+	return rq;
+}
+
+/*
+ * No available requests for this queue, unplug the device and wait for some
+ * requests to become available.
+ *
+ * Called with q->queue_lock held, and returns with it unlocked.
+ */
+static struct request *get_request_wait(request_queue_t *q, int rw,
+					struct bio *bio)
+{
+	struct request *rq;
+
+	rq = get_request(q, rw, bio, GFP_NOIO);
+	while (!rq) {
+		DEFINE_WAIT(wait);
+		struct request_list *rl = &q->rq;
+
+		prepare_to_wait_exclusive(&rl->wait[rw], &wait,
+				TASK_UNINTERRUPTIBLE);
+
+		rq = get_request(q, rw, bio, GFP_NOIO);
+
+		if (!rq) {
+			struct io_context *ioc;
+
+			__generic_unplug_device(q);
+			spin_unlock_irq(q->queue_lock);
+			io_schedule();
+
+			/*
+			 * After sleeping, we become a "batching" process and
+			 * will be able to allocate at least one request, and
+			 * up to a big batch of them for a small period time.
+			 * See ioc_batching, ioc_set_batching
+			 */
+			ioc = current_io_context(GFP_NOIO);
+			ioc_set_batching(q, ioc);
+
+			spin_lock_irq(q->queue_lock);
+		}
+		finish_wait(&rl->wait[rw], &wait);
+	}
+
+	return rq;
+}
+
+struct request *blk_get_request(request_queue_t *q, int rw, gfp_t gfp_mask)
+{
+	struct request *rq;
+
+	BUG_ON(rw != READ && rw != WRITE);
+
+	spin_lock_irq(q->queue_lock);
+	if (gfp_mask & __GFP_WAIT) {
+		rq = get_request_wait(q, rw, NULL);
+	} else {
+		rq = get_request(q, rw, NULL, gfp_mask);
+		if (!rq)
+			spin_unlock_irq(q->queue_lock);
+	}
+	/* q->queue_lock is unlocked at this point */
+
+	return rq;
+}
+EXPORT_SYMBOL(blk_get_request);
+
+/**
+ * blk_requeue_request - put a request back on queue
+ * @q:		request queue where request should be inserted
+ * @rq:		request to be inserted
+ *
+ * Description:
+ *    Drivers often keep queueing requests until the hardware cannot accept
+ *    more, when that condition happens we need to put the request back
+ *    on the queue. Must be called with queue lock held.
+ */
+void blk_requeue_request(request_queue_t *q, struct request *rq)
+{
+	if (blk_rq_tagged(rq))
+		blk_queue_end_tag(q, rq);
+
+	elv_requeue_request(q, rq);
+}
+
+EXPORT_SYMBOL(blk_requeue_request);
+
+/**
+ * blk_insert_request - insert a special request in to a request queue
+ * @q:		request queue where request should be inserted
+ * @rq:		request to be inserted
+ * @at_head:	insert request at head or tail of queue
+ * @data:	private data
+ *
+ * Description:
+ *    Many block devices need to execute commands asynchronously, so they don't
+ *    block the whole kernel from preemption during request execution.  This is
+ *    accomplished normally by inserting aritficial requests tagged as
+ *    REQ_SPECIAL in to the corresponding request queue, and letting them be
+ *    scheduled for actual execution by the request queue.
+ *
+ *    We have the option of inserting the head or the tail of the queue.
+ *    Typically we use the tail for new ioctls and so forth.  We use the head
+ *    of the queue for things like a QUEUE_FULL message from a device, or a
+ *    host that is unable to accept a particular command.
+ */
+void blk_insert_request(request_queue_t *q, struct request *rq,
+			int at_head, void *data)
+{
+	int where = at_head ? ELEVATOR_INSERT_FRONT : ELEVATOR_INSERT_BACK;
+	unsigned long flags;
+
+	/*
+	 * tell I/O scheduler that this isn't a regular read/write (ie it
+	 * must not attempt merges on this) and that it acts as a soft
+	 * barrier
+	 */
+	rq->flags |= REQ_SPECIAL | REQ_SOFTBARRIER;
+
+	rq->special = data;
+
+	spin_lock_irqsave(q->queue_lock, flags);
+
+	/*
+	 * If command is tagged, release the tag
+	 */
+	if (blk_rq_tagged(rq))
+		blk_queue_end_tag(q, rq);
+
+	drive_stat_acct(rq, rq->nr_sectors, 1);
+	__elv_add_request(q, rq, where, 0);
+
+	if (blk_queue_plugged(q))
+		__generic_unplug_device(q);
+	else
+		q->request_fn(q);
+	spin_unlock_irqrestore(q->queue_lock, flags);
+}
+
+EXPORT_SYMBOL(blk_insert_request);
+
+/**
+ * blk_rq_map_user - map user data to a request, for REQ_BLOCK_PC usage
+ * @q:		request queue where request should be inserted
+ * @rq:		request structure to fill
+ * @ubuf:	the user buffer
+ * @len:	length of user data
+ *
+ * Description:
+ *    Data will be mapped directly for zero copy io, if possible. Otherwise
+ *    a kernel bounce buffer is used.
+ *
+ *    A matching blk_rq_unmap_user() must be issued at the end of io, while
+ *    still in process context.
+ *
+ *    Note: The mapped bio may need to be bounced through blk_queue_bounce()
+ *    before being submitted to the device, as pages mapped may be out of
+ *    reach. It's the callers responsibility to make sure this happens. The
+ *    original bio must be passed back in to blk_rq_unmap_user() for proper
+ *    unmapping.
+ */
+int blk_rq_map_user(request_queue_t *q, struct request *rq, void __user *ubuf,
+		    unsigned int len)
+{
+	unsigned long uaddr;
+	struct bio *bio;
+	int reading;
+
+	if (len > (q->max_sectors << 9))
+		return -EINVAL;
+	if (!len || !ubuf)
+		return -EINVAL;
+
+	reading = rq_data_dir(rq) == READ;
+
+	/*
+	 * if alignment requirement is satisfied, map in user pages for
+	 * direct dma. else, set up kernel bounce buffers
+	 */
+	uaddr = (unsigned long) ubuf;
+	if (!(uaddr & queue_dma_alignment(q)) && !(len & queue_dma_alignment(q)))
+		bio = bio_map_user(q, NULL, uaddr, len, reading);
+	else
+		bio = bio_copy_user(q, uaddr, len, reading);
+
+	if (!IS_ERR(bio)) {
+		rq->bio = rq->biotail = bio;
+		blk_rq_bio_prep(q, rq, bio);
+
+		rq->buffer = rq->data = NULL;
+		rq->data_len = len;
+		return 0;
+	}
+
+	/*
+	 * bio is the err-ptr
+	 */
+	return PTR_ERR(bio);
+}
+
+EXPORT_SYMBOL(blk_rq_map_user);
+
+/**
+ * blk_rq_map_user_iov - map user data to a request, for REQ_BLOCK_PC usage
+ * @q:		request queue where request should be inserted
+ * @rq:		request to map data to
+ * @iov:	pointer to the iovec
+ * @iov_count:	number of elements in the iovec
+ *
+ * Description:
+ *    Data will be mapped directly for zero copy io, if possible. Otherwise
+ *    a kernel bounce buffer is used.
+ *
+ *    A matching blk_rq_unmap_user() must be issued at the end of io, while
+ *    still in process context.
+ *
+ *    Note: The mapped bio may need to be bounced through blk_queue_bounce()
+ *    before being submitted to the device, as pages mapped may be out of
+ *    reach. It's the callers responsibility to make sure this happens. The
+ *    original bio must be passed back in to blk_rq_unmap_user() for proper
+ *    unmapping.
+ */
+int blk_rq_map_user_iov(request_queue_t *q, struct request *rq,
+			struct sg_iovec *iov, int iov_count)
+{
+	struct bio *bio;
+
+	if (!iov || iov_count <= 0)
+		return -EINVAL;
+
+	/* we don't allow misaligned data like bio_map_user() does.  If the
+	 * user is using sg, they're expected to know the alignment constraints
+	 * and respect them accordingly */
+	bio = bio_map_user_iov(q, NULL, iov, iov_count, rq_data_dir(rq)== READ);
+	if (IS_ERR(bio))
+		return PTR_ERR(bio);
+
+	rq->bio = rq->biotail = bio;
+	blk_rq_bio_prep(q, rq, bio);
+	rq->buffer = rq->data = NULL;
+	rq->data_len = bio->bi_size;
+	return 0;
+}
+
+EXPORT_SYMBOL(blk_rq_map_user_iov);
+
+/**
+ * blk_rq_unmap_user - unmap a request with user data
+ * @bio:	bio to be unmapped
+ * @ulen:	length of user buffer
+ *
+ * Description:
+ *    Unmap a bio previously mapped by blk_rq_map_user().
+ */
+int blk_rq_unmap_user(struct bio *bio, unsigned int ulen)
+{
+	int ret = 0;
+
+	if (bio) {
+		if (bio_flagged(bio, BIO_USER_MAPPED))
+			bio_unmap_user(bio);
+		else
+			ret = bio_uncopy_user(bio);
+	}
+
+	return 0;
+}
+
+EXPORT_SYMBOL(blk_rq_unmap_user);
+
+/**
+ * blk_rq_map_kern - map kernel data to a request, for REQ_BLOCK_PC usage
+ * @q:		request queue where request should be inserted
+ * @rq:		request to fill
+ * @kbuf:	the kernel buffer
+ * @len:	length of user data
+ * @gfp_mask:	memory allocation flags
+ */
+int blk_rq_map_kern(request_queue_t *q, struct request *rq, void *kbuf,
+		    unsigned int len, gfp_t gfp_mask)
+{
+	struct bio *bio;
+
+	if (len > (q->max_sectors << 9))
+		return -EINVAL;
+	if (!len || !kbuf)
+		return -EINVAL;
+
+	bio = bio_map_kern(q, kbuf, len, gfp_mask);
+	if (IS_ERR(bio))
+		return PTR_ERR(bio);
+
+	if (rq_data_dir(rq) == WRITE)
+		bio->bi_rw |= (1 << BIO_RW);
+
+	rq->bio = rq->biotail = bio;
+	blk_rq_bio_prep(q, rq, bio);
+
+	rq->buffer = rq->data = NULL;
+	rq->data_len = len;
+	return 0;
+}
+
+EXPORT_SYMBOL(blk_rq_map_kern);
+
+/**
+ * blk_execute_rq_nowait - insert a request into queue for execution
+ * @q:		queue to insert the request in
+ * @bd_disk:	matching gendisk
+ * @rq:		request to insert
+ * @at_head:    insert request at head or tail of queue
+ * @done:	I/O completion handler
+ *
+ * Description:
+ *    Insert a fully prepared request at the back of the io scheduler queue
+ *    for execution.  Don't wait for completion.
+ */
+void blk_execute_rq_nowait(request_queue_t *q, struct gendisk *bd_disk,
+			   struct request *rq, int at_head,
+			   void (*done)(struct request *))
+{
+	int where = at_head ? ELEVATOR_INSERT_FRONT : ELEVATOR_INSERT_BACK;
+
+	rq->rq_disk = bd_disk;
+	rq->flags |= REQ_NOMERGE;
+	rq->end_io = done;
+	elv_add_request(q, rq, where, 1);
+	generic_unplug_device(q);
+}
+
+/**
+ * blk_execute_rq - insert a request into queue for execution
+ * @q:		queue to insert the request in
+ * @bd_disk:	matching gendisk
+ * @rq:		request to insert
+ * @at_head:    insert request at head or tail of queue
+ *
+ * Description:
+ *    Insert a fully prepared request at the back of the io scheduler queue
+ *    for execution and wait for completion.
+ */
+int blk_execute_rq(request_queue_t *q, struct gendisk *bd_disk,
+		   struct request *rq, int at_head)
+{
+	DECLARE_COMPLETION(wait);
+	char sense[SCSI_SENSE_BUFFERSIZE];
+	int err = 0;
+
+	/*
+	 * we need an extra reference to the request, so we can look at
+	 * it after io completion
+	 */
+	rq->ref_count++;
+
+	if (!rq->sense) {
+		memset(sense, 0, sizeof(sense));
+		rq->sense = sense;
+		rq->sense_len = 0;
+	}
+
+	rq->waiting = &wait;
+	blk_execute_rq_nowait(q, bd_disk, rq, at_head, blk_end_sync_rq);
+	wait_for_completion(&wait);
+	rq->waiting = NULL;
+
+	if (rq->errors)
+		err = -EIO;
+
+	return err;
+}
+
+EXPORT_SYMBOL(blk_execute_rq);
+
+/**
+ * blkdev_issue_flush - queue a flush
+ * @bdev:	blockdev to issue flush for
+ * @error_sector:	error sector
+ *
+ * Description:
+ *    Issue a flush for the block device in question. Caller can supply
+ *    room for storing the error offset in case of a flush error, if they
+ *    wish to.  Caller must run wait_for_completion() on its own.
+ */
+int blkdev_issue_flush(struct block_device *bdev, sector_t *error_sector)
+{
+	request_queue_t *q;
+
+	if (bdev->bd_disk == NULL)
+		return -ENXIO;
+
+	q = bdev_get_queue(bdev);
+	if (!q)
+		return -ENXIO;
+	if (!q->issue_flush_fn)
+		return -EOPNOTSUPP;
+
+	return q->issue_flush_fn(q, bdev->bd_disk, error_sector);
+}
+
+EXPORT_SYMBOL(blkdev_issue_flush);
+
+static void drive_stat_acct(struct request *rq, int nr_sectors, int new_io)
+{
+	int rw = rq_data_dir(rq);
+
+	if (!blk_fs_request(rq) || !rq->rq_disk)
+		return;
+
+	if (!new_io) {
+		__disk_stat_inc(rq->rq_disk, merges[rw]);
+	} else {
+		disk_round_stats(rq->rq_disk);
+		rq->rq_disk->in_flight++;
+	}
+}
+
+/*
+ * add-request adds a request to the linked list.
+ * queue lock is held and interrupts disabled, as we muck with the
+ * request queue list.
+ */
+static inline void add_request(request_queue_t * q, struct request * req)
+{
+	drive_stat_acct(req, req->nr_sectors, 1);
+
+	if (q->activity_fn)
+		q->activity_fn(q->activity_data, rq_data_dir(req));
+
+	/*
+	 * elevator indicated where it wants this request to be
+	 * inserted at elevator_merge time
+	 */
+	__elv_add_request(q, req, ELEVATOR_INSERT_SORT, 0);
+}
+ 
+/*
+ * disk_round_stats()	- Round off the performance stats on a struct
+ * disk_stats.
+ *
+ * The average IO queue length and utilisation statistics are maintained
+ * by observing the current state of the queue length and the amount of
+ * time it has been in this state for.
+ *
+ * Normally, that accounting is done on IO completion, but that can result
+ * in more than a second's worth of IO being accounted for within any one
+ * second, leading to >100% utilisation.  To deal with that, we call this
+ * function to do a round-off before returning the results when reading
+ * /proc/diskstats.  This accounts immediately for all queue usage up to
+ * the current jiffies and restarts the counters again.
+ */
+void disk_round_stats(struct gendisk *disk)
+{
+	unsigned long now = jiffies;
+
+	if (now == disk->stamp)
+		return;
+
+	if (disk->in_flight) {
+		__disk_stat_add(disk, time_in_queue,
+				disk->in_flight * (now - disk->stamp));
+		__disk_stat_add(disk, io_ticks, (now - disk->stamp));
+	}
+	disk->stamp = now;
+}
+
+/*
+ * queue lock must be held
+ */
+static void __blk_put_request(request_queue_t *q, struct request *req)
+{
+	struct request_list *rl = req->rl;
+
+	if (unlikely(!q))
+		return;
+	if (unlikely(--req->ref_count))
+		return;
+
+	elv_completed_request(q, req);
+
+	req->rq_status = RQ_INACTIVE;
+	req->rl = NULL;
+
+	/*
+	 * Request may not have originated from ll_rw_blk. if not,
+	 * it didn't come out of our reserved rq pools
+	 */
+	if (rl) {
+		int rw = rq_data_dir(req);
+		int priv = req->flags & REQ_ELVPRIV;
+
+		BUG_ON(!list_empty(&req->queuelist));
+
+		blk_free_request(q, req);
+		freed_request(q, rw, priv);
+	}
+}
+
+void blk_put_request(struct request *req)
+{
+	unsigned long flags;
+	request_queue_t *q = req->q;
+
+	/*
+	 * Gee, IDE calls in w/ NULL q.  Fix IDE and remove the
+	 * following if (q) test.
+	 */
+	if (q) {
+		spin_lock_irqsave(q->queue_lock, flags);
+		__blk_put_request(q, req);
+		spin_unlock_irqrestore(q->queue_lock, flags);
+	}
+}
+
+EXPORT_SYMBOL(blk_put_request);
+
+/**
+ * blk_end_sync_rq - executes a completion event on a request
+ * @rq: request to complete
+ */
+void blk_end_sync_rq(struct request *rq)
+{
+	struct completion *waiting = rq->waiting;
+
+	rq->waiting = NULL;
+	__blk_put_request(rq->q, rq);
+
+	/*
+	 * complete last, if this is a stack request the process (and thus
+	 * the rq pointer) could be invalid right after this complete()
+	 */
+	complete(waiting);
+}
+EXPORT_SYMBOL(blk_end_sync_rq);
+
+/**
+ * blk_congestion_wait - wait for a queue to become uncongested
+ * @rw: READ or WRITE
+ * @timeout: timeout in jiffies
+ *
+ * Waits for up to @timeout jiffies for a queue (any queue) to exit congestion.
+ * If no queues are congested then just wait for the next request to be
+ * returned.
+ */
+long blk_congestion_wait(int rw, long timeout)
+{
+	long ret;
+	DEFINE_WAIT(wait);
+	wait_queue_head_t *wqh = &congestion_wqh[rw];
+
+	prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
+	ret = io_schedule_timeout(timeout);
+	finish_wait(wqh, &wait);
+	return ret;
+}
+
+EXPORT_SYMBOL(blk_congestion_wait);
+
+/*
+ * Has to be called with the request spinlock acquired
+ */
+static int attempt_merge(request_queue_t *q, struct request *req,
+			  struct request *next)
+{
+	if (!rq_mergeable(req) || !rq_mergeable(next))
+		return 0;
+
+	/*
+	 * not contigious
+	 */
+	if (req->sector + req->nr_sectors != next->sector)
+		return 0;
+
+	if (rq_data_dir(req) != rq_data_dir(next)
+	    || req->rq_disk != next->rq_disk
+	    || next->waiting || next->special)
+		return 0;
+
+	/*
+	 * If we are allowed to merge, then append bio list
+	 * from next to rq and release next. merge_requests_fn
+	 * will have updated segment counts, update sector
+	 * counts here.
+	 */
+	if (!q->merge_requests_fn(q, req, next))
+		return 0;
+
+	/*
+	 * At this point we have either done a back merge
+	 * or front merge. We need the smaller start_time of
+	 * the merged requests to be the current request
+	 * for accounting purposes.
+	 */
+	if (time_after(req->start_time, next->start_time))
+		req->start_time = next->start_time;
+
+	req->biotail->bi_next = next->bio;
+	req->biotail = next->biotail;
+
+	req->nr_sectors = req->hard_nr_sectors += next->hard_nr_sectors;
+
+	elv_merge_requests(q, req, next);
+
+	if (req->rq_disk) {
+		disk_round_stats(req->rq_disk);
+		req->rq_disk->in_flight--;
+	}
+
+	req->ioprio = ioprio_best(req->ioprio, next->ioprio);
+
+	__blk_put_request(q, next);
+	return 1;
+}
+
+static inline int attempt_back_merge(request_queue_t *q, struct request *rq)
+{
+	struct request *next = elv_latter_request(q, rq);
+
+	if (next)
+		return attempt_merge(q, rq, next);
+
+	return 0;
+}
+
+static inline int attempt_front_merge(request_queue_t *q, struct request *rq)
+{
+	struct request *prev = elv_former_request(q, rq);
+
+	if (prev)
+		return attempt_merge(q, prev, rq);
+
+	return 0;
+}
+
+/**
+ * blk_attempt_remerge  - attempt to remerge active head with next request
+ * @q:    The &request_queue_t belonging to the device
+ * @rq:   The head request (usually)
+ *
+ * Description:
+ *    For head-active devices, the queue can easily be unplugged so quickly
+ *    that proper merging is not done on the front request. This may hurt
+ *    performance greatly for some devices. The block layer cannot safely
+ *    do merging on that first request for these queues, but the driver can
+ *    call this function and make it happen any way. Only the driver knows
+ *    when it is safe to do so.
+ **/
+void blk_attempt_remerge(request_queue_t *q, struct request *rq)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(q->queue_lock, flags);
+	attempt_back_merge(q, rq);
+	spin_unlock_irqrestore(q->queue_lock, flags);
+}
+
+EXPORT_SYMBOL(blk_attempt_remerge);
+
+static int __make_request(request_queue_t *q, struct bio *bio)
+{
+	struct request *req;
+	int el_ret, rw, nr_sectors, cur_nr_sectors, barrier, err, sync;
+	unsigned short prio;
+	sector_t sector;
+
+	sector = bio->bi_sector;
+	nr_sectors = bio_sectors(bio);
+	cur_nr_sectors = bio_cur_sectors(bio);
+	prio = bio_prio(bio);
+
+	rw = bio_data_dir(bio);
+	sync = bio_sync(bio);
+
+	/*
+	 * low level driver can indicate that it wants pages above a
+	 * certain limit bounced to low memory (ie for highmem, or even
+	 * ISA dma in theory)
+	 */
+	blk_queue_bounce(q, &bio);
+
+	spin_lock_prefetch(q->queue_lock);
+
+	barrier = bio_barrier(bio);
+	if (unlikely(barrier) && (q->ordered == QUEUE_ORDERED_NONE)) {
+		err = -EOPNOTSUPP;
+		goto end_io;
+	}
+
+	spin_lock_irq(q->queue_lock);
+
+	if (unlikely(barrier) || elv_queue_empty(q))
+		goto get_rq;
+
+	el_ret = elv_merge(q, &req, bio);
+	switch (el_ret) {
+		case ELEVATOR_BACK_MERGE:
+			BUG_ON(!rq_mergeable(req));
+
+			if (!q->back_merge_fn(q, req, bio))
+				break;
+
+			req->biotail->bi_next = bio;
+			req->biotail = bio;
+			req->nr_sectors = req->hard_nr_sectors += nr_sectors;
+			req->ioprio = ioprio_best(req->ioprio, prio);
+			drive_stat_acct(req, nr_sectors, 0);
+			if (!attempt_back_merge(q, req))
+				elv_merged_request(q, req);
+			goto out;
+
+		case ELEVATOR_FRONT_MERGE:
+			BUG_ON(!rq_mergeable(req));
+
+			if (!q->front_merge_fn(q, req, bio))
+				break;
+
+			bio->bi_next = req->bio;
+			req->bio = bio;
+
+			/*
+			 * may not be valid. if the low level driver said
+			 * it didn't need a bounce buffer then it better
+			 * not touch req->buffer either...
+			 */
+			req->buffer = bio_data(bio);
+			req->current_nr_sectors = cur_nr_sectors;
+			req->hard_cur_sectors = cur_nr_sectors;
+			req->sector = req->hard_sector = sector;
+			req->nr_sectors = req->hard_nr_sectors += nr_sectors;
+			req->ioprio = ioprio_best(req->ioprio, prio);
+			drive_stat_acct(req, nr_sectors, 0);
+			if (!attempt_front_merge(q, req))
+				elv_merged_request(q, req);
+			goto out;
+
+		/* ELV_NO_MERGE: elevator says don't/can't merge. */
+		default:
+			;
+	}
+
+get_rq:
+	/*
+	 * Grab a free request. This is might sleep but can not fail.
+	 * Returns with the queue unlocked.
+	 */
+	req = get_request_wait(q, rw, bio);
+
+	/*
+	 * After dropping the lock and possibly sleeping here, our request
+	 * may now be mergeable after it had proven unmergeable (above).
+	 * We don't worry about that case for efficiency. It won't happen
+	 * often, and the elevators are able to handle it.
+	 */
+
+	req->flags |= REQ_CMD;
+
+	/*
+	 * inherit FAILFAST from bio (for read-ahead, and explicit FAILFAST)
+	 */
+	if (bio_rw_ahead(bio) || bio_failfast(bio))
+		req->flags |= REQ_FAILFAST;
+
+	/*
+	 * REQ_BARRIER implies no merging, but lets make it explicit
+	 */
+	if (unlikely(barrier))
+		req->flags |= (REQ_HARDBARRIER | REQ_NOMERGE);
+
+	req->errors = 0;
+	req->hard_sector = req->sector = sector;
+	req->hard_nr_sectors = req->nr_sectors = nr_sectors;
+	req->current_nr_sectors = req->hard_cur_sectors = cur_nr_sectors;
+	req->nr_phys_segments = bio_phys_segments(q, bio);
+	req->nr_hw_segments = bio_hw_segments(q, bio);
+	req->buffer = bio_data(bio);	/* see ->buffer comment above */
+	req->waiting = NULL;
+	req->bio = req->biotail = bio;
+	req->ioprio = prio;
+	req->rq_disk = bio->bi_bdev->bd_disk;
+	req->start_time = jiffies;
+
+	spin_lock_irq(q->queue_lock);
+	if (elv_queue_empty(q))
+		blk_plug_device(q);
+	add_request(q, req);
+out:
+	if (sync)
+		__generic_unplug_device(q);
+
+	spin_unlock_irq(q->queue_lock);
+	return 0;
+
+end_io:
+	bio_endio(bio, nr_sectors << 9, err);
+	return 0;
+}
+
+/*
+ * If bio->bi_dev is a partition, remap the location
+ */
+static inline void blk_partition_remap(struct bio *bio)
+{
+	struct block_device *bdev = bio->bi_bdev;
+
+	if (bdev != bdev->bd_contains) {
+		struct hd_struct *p = bdev->bd_part;
+		const int rw = bio_data_dir(bio);
+
+		p->sectors[rw] += bio_sectors(bio);
+		p->ios[rw]++;
+
+		bio->bi_sector += p->start_sect;
+		bio->bi_bdev = bdev->bd_contains;
+	}
+}
+
+static void handle_bad_sector(struct bio *bio)
+{
+	char b[BDEVNAME_SIZE];
+
+	printk(KERN_INFO "attempt to access beyond end of device\n");
+	printk(KERN_INFO "%s: rw=%ld, want=%Lu, limit=%Lu\n",
+			bdevname(bio->bi_bdev, b),
+			bio->bi_rw,
+			(unsigned long long)bio->bi_sector + bio_sectors(bio),
+			(long long)(bio->bi_bdev->bd_inode->i_size >> 9));
+
+	set_bit(BIO_EOF, &bio->bi_flags);
+}
+
+/**
+ * generic_make_request: hand a buffer to its device driver for I/O
+ * @bio:  The bio describing the location in memory and on the device.
+ *
+ * generic_make_request() is used to make I/O requests of block
+ * devices. It is passed a &struct bio, which describes the I/O that needs
+ * to be done.
+ *
+ * generic_make_request() does not return any status.  The
+ * success/failure status of the request, along with notification of
+ * completion, is delivered asynchronously through the bio->bi_end_io
+ * function described (one day) else where.
+ *
+ * The caller of generic_make_request must make sure that bi_io_vec
+ * are set to describe the memory buffer, and that bi_dev and bi_sector are
+ * set to describe the device address, and the
+ * bi_end_io and optionally bi_private are set to describe how
+ * completion notification should be signaled.
+ *
+ * generic_make_request and the drivers it calls may use bi_next if this
+ * bio happens to be merged with someone else, and may change bi_dev and
+ * bi_sector for remaps as it sees fit.  So the values of these fields
+ * should NOT be depended on after the call to generic_make_request.
+ */
+void generic_make_request(struct bio *bio)
+{
+	request_queue_t *q;
+	sector_t maxsector;
+	int ret, nr_sectors = bio_sectors(bio);
+
+	might_sleep();
+	/* Test device or partition size, when known. */
+	maxsector = bio->bi_bdev->bd_inode->i_size >> 9;
+	if (maxsector) {
+		sector_t sector = bio->bi_sector;
+
+		if (maxsector < nr_sectors || maxsector - nr_sectors < sector) {
+			/*
+			 * This may well happen - the kernel calls bread()
+			 * without checking the size of the device, e.g., when
+			 * mounting a device.
+			 */
+			handle_bad_sector(bio);
+			goto end_io;
+		}
+	}
+
+	/*
+	 * Resolve the mapping until finished. (drivers are
+	 * still free to implement/resolve their own stacking
+	 * by explicitly returning 0)
+	 *
+	 * NOTE: we don't repeat the blk_size check for each new device.
+	 * Stacking drivers are expected to know what they are doing.
+	 */
+	do {
+		char b[BDEVNAME_SIZE];
+
+		q = bdev_get_queue(bio->bi_bdev);
+		if (!q) {
+			printk(KERN_ERR
+			       "generic_make_request: Trying to access "
+				"nonexistent block-device %s (%Lu)\n",
+				bdevname(bio->bi_bdev, b),
+				(long long) bio->bi_sector);
+end_io:
+			bio_endio(bio, bio->bi_size, -EIO);
+			break;
+		}
+
+		if (unlikely(bio_sectors(bio) > q->max_hw_sectors)) {
+			printk("bio too big device %s (%u > %u)\n", 
+				bdevname(bio->bi_bdev, b),
+				bio_sectors(bio),
+				q->max_hw_sectors);
+			goto end_io;
+		}
+
+		if (unlikely(test_bit(QUEUE_FLAG_DEAD, &q->queue_flags)))
+			goto end_io;
+
+		/*
+		 * If this device has partitions, remap block n
+		 * of partition p to block n+start(p) of the disk.
+		 */
+		blk_partition_remap(bio);
+
+		ret = q->make_request_fn(q, bio);
+	} while (ret);
+}
+
+EXPORT_SYMBOL(generic_make_request);
+
+/**
+ * submit_bio: submit a bio to the block device layer for I/O
+ * @rw: whether to %READ or %WRITE, or maybe to %READA (read ahead)
+ * @bio: The &struct bio which describes the I/O
+ *
+ * submit_bio() is very similar in purpose to generic_make_request(), and
+ * uses that function to do most of the work. Both are fairly rough
+ * interfaces, @bio must be presetup and ready for I/O.
+ *
+ */
+void submit_bio(int rw, struct bio *bio)
+{
+	int count = bio_sectors(bio);
+
+	BIO_BUG_ON(!bio->bi_size);
+	BIO_BUG_ON(!bio->bi_io_vec);
+	bio->bi_rw |= rw;
+	if (rw & WRITE)
+		mod_page_state(pgpgout, count);
+	else
+		mod_page_state(pgpgin, count);
+
+	if (unlikely(block_dump)) {
+		char b[BDEVNAME_SIZE];
+		printk(KERN_DEBUG "%s(%d): %s block %Lu on %s\n",
+			current->comm, current->pid,
+			(rw & WRITE) ? "WRITE" : "READ",
+			(unsigned long long)bio->bi_sector,
+			bdevname(bio->bi_bdev,b));
+	}
+
+	generic_make_request(bio);
+}
+
+EXPORT_SYMBOL(submit_bio);
+
+static void blk_recalc_rq_segments(struct request *rq)
+{
+	struct bio *bio, *prevbio = NULL;
+	int nr_phys_segs, nr_hw_segs;
+	unsigned int phys_size, hw_size;
+	request_queue_t *q = rq->q;
+
+	if (!rq->bio)
+		return;
+
+	phys_size = hw_size = nr_phys_segs = nr_hw_segs = 0;
+	rq_for_each_bio(bio, rq) {
+		/* Force bio hw/phys segs to be recalculated. */
+		bio->bi_flags &= ~(1 << BIO_SEG_VALID);
+
+		nr_phys_segs += bio_phys_segments(q, bio);
+		nr_hw_segs += bio_hw_segments(q, bio);
+		if (prevbio) {
+			int pseg = phys_size + prevbio->bi_size + bio->bi_size;
+			int hseg = hw_size + prevbio->bi_size + bio->bi_size;
+
+			if (blk_phys_contig_segment(q, prevbio, bio) &&
+			    pseg <= q->max_segment_size) {
+				nr_phys_segs--;
+				phys_size += prevbio->bi_size + bio->bi_size;
+			} else
+				phys_size = 0;
+
+			if (blk_hw_contig_segment(q, prevbio, bio) &&
+			    hseg <= q->max_segment_size) {
+				nr_hw_segs--;
+				hw_size += prevbio->bi_size + bio->bi_size;
+			} else
+				hw_size = 0;
+		}
+		prevbio = bio;
+	}
+
+	rq->nr_phys_segments = nr_phys_segs;
+	rq->nr_hw_segments = nr_hw_segs;
+}
+
+static void blk_recalc_rq_sectors(struct request *rq, int nsect)
+{
+	if (blk_fs_request(rq)) {
+		rq->hard_sector += nsect;
+		rq->hard_nr_sectors -= nsect;
+
+		/*
+		 * Move the I/O submission pointers ahead if required.
+		 */
+		if ((rq->nr_sectors >= rq->hard_nr_sectors) &&
+		    (rq->sector <= rq->hard_sector)) {
+			rq->sector = rq->hard_sector;
+			rq->nr_sectors = rq->hard_nr_sectors;
+			rq->hard_cur_sectors = bio_cur_sectors(rq->bio);
+			rq->current_nr_sectors = rq->hard_cur_sectors;
+			rq->buffer = bio_data(rq->bio);
+		}
+
+		/*
+		 * if total number of sectors is less than the first segment
+		 * size, something has gone terribly wrong
+		 */
+		if (rq->nr_sectors < rq->current_nr_sectors) {
+			printk("blk: request botched\n");
+			rq->nr_sectors = rq->current_nr_sectors;
+		}
+	}
+}
+
+static int __end_that_request_first(struct request *req, int uptodate,
+				    int nr_bytes)
+{
+	int total_bytes, bio_nbytes, error, next_idx = 0;
+	struct bio *bio;
+
+	/*
+	 * extend uptodate bool to allow < 0 value to be direct io error
+	 */
+	error = 0;
+	if (end_io_error(uptodate))
+		error = !uptodate ? -EIO : uptodate;
+
+	/*
+	 * for a REQ_BLOCK_PC request, we want to carry any eventual
+	 * sense key with us all the way through
+	 */
+	if (!blk_pc_request(req))
+		req->errors = 0;
+
+	if (!uptodate) {
+		if (blk_fs_request(req) && !(req->flags & REQ_QUIET))
+			printk("end_request: I/O error, dev %s, sector %llu\n",
+				req->rq_disk ? req->rq_disk->disk_name : "?",
+				(unsigned long long)req->sector);
+	}
+
+	if (blk_fs_request(req) && req->rq_disk) {
+		const int rw = rq_data_dir(req);
+
+		__disk_stat_add(req->rq_disk, sectors[rw], nr_bytes >> 9);
+	}
+
+	total_bytes = bio_nbytes = 0;
+	while ((bio = req->bio) != NULL) {
+		int nbytes;
+
+		if (nr_bytes >= bio->bi_size) {
+			req->bio = bio->bi_next;
+			nbytes = bio->bi_size;
+			bio_endio(bio, nbytes, error);
+			next_idx = 0;
+			bio_nbytes = 0;
+		} else {
+			int idx = bio->bi_idx + next_idx;
+
+			if (unlikely(bio->bi_idx >= bio->bi_vcnt)) {
+				blk_dump_rq_flags(req, "__end_that");
+				printk("%s: bio idx %d >= vcnt %d\n",
+						__FUNCTION__,
+						bio->bi_idx, bio->bi_vcnt);
+				break;
+			}
+
+			nbytes = bio_iovec_idx(bio, idx)->bv_len;
+			BIO_BUG_ON(nbytes > bio->bi_size);
+
+			/*
+			 * not a complete bvec done
+			 */
+			if (unlikely(nbytes > nr_bytes)) {
+				bio_nbytes += nr_bytes;
+				total_bytes += nr_bytes;
+				break;
+			}
+
+			/*
+			 * advance to the next vector
+			 */
+			next_idx++;
+			bio_nbytes += nbytes;
+		}
+
+		total_bytes += nbytes;
+		nr_bytes -= nbytes;
+
+		if ((bio = req->bio)) {
+			/*
+			 * end more in this run, or just return 'not-done'
+			 */
+			if (unlikely(nr_bytes <= 0))
+				break;
+		}
+	}
+
+	/*
+	 * completely done
+	 */
+	if (!req->bio)
+		return 0;
+
+	/*
+	 * if the request wasn't completed, update state
+	 */
+	if (bio_nbytes) {
+		bio_endio(bio, bio_nbytes, error);
+		bio->bi_idx += next_idx;
+		bio_iovec(bio)->bv_offset += nr_bytes;
+		bio_iovec(bio)->bv_len -= nr_bytes;
+	}
+
+	blk_recalc_rq_sectors(req, total_bytes >> 9);
+	blk_recalc_rq_segments(req);
+	return 1;
+}
+
+/**
+ * end_that_request_first - end I/O on a request
+ * @req:      the request being processed
+ * @uptodate: 1 for success, 0 for I/O error, < 0 for specific error
+ * @nr_sectors: number of sectors to end I/O on
+ *
+ * Description:
+ *     Ends I/O on a number of sectors attached to @req, and sets it up
+ *     for the next range of segments (if any) in the cluster.
+ *
+ * Return:
+ *     0 - we are done with this request, call end_that_request_last()
+ *     1 - still buffers pending for this request
+ **/
+int end_that_request_first(struct request *req, int uptodate, int nr_sectors)
+{
+	return __end_that_request_first(req, uptodate, nr_sectors << 9);
+}
+
+EXPORT_SYMBOL(end_that_request_first);
+
+/**
+ * end_that_request_chunk - end I/O on a request
+ * @req:      the request being processed
+ * @uptodate: 1 for success, 0 for I/O error, < 0 for specific error
+ * @nr_bytes: number of bytes to complete
+ *
+ * Description:
+ *     Ends I/O on a number of bytes attached to @req, and sets it up
+ *     for the next range of segments (if any). Like end_that_request_first(),
+ *     but deals with bytes instead of sectors.
+ *
+ * Return:
+ *     0 - we are done with this request, call end_that_request_last()
+ *     1 - still buffers pending for this request
+ **/
+int end_that_request_chunk(struct request *req, int uptodate, int nr_bytes)
+{
+	return __end_that_request_first(req, uptodate, nr_bytes);
+}
+
+EXPORT_SYMBOL(end_that_request_chunk);
+
+/*
+ * queue lock must be held
+ */
+void end_that_request_last(struct request *req)
+{
+	struct gendisk *disk = req->rq_disk;
+
+	if (unlikely(laptop_mode) && blk_fs_request(req))
+		laptop_io_completion();
+
+	if (disk && blk_fs_request(req)) {
+		unsigned long duration = jiffies - req->start_time;
+		const int rw = rq_data_dir(req);
+
+		__disk_stat_inc(disk, ios[rw]);
+		__disk_stat_add(disk, ticks[rw], duration);
+		disk_round_stats(disk);
+		disk->in_flight--;
+	}
+	if (req->end_io)
+		req->end_io(req);
+	else
+		__blk_put_request(req->q, req);
+}
+
+EXPORT_SYMBOL(end_that_request_last);
+
+void end_request(struct request *req, int uptodate)
+{
+	if (!end_that_request_first(req, uptodate, req->hard_cur_sectors)) {
+		add_disk_randomness(req->rq_disk);
+		blkdev_dequeue_request(req);
+		end_that_request_last(req);
+	}
+}
+
+EXPORT_SYMBOL(end_request);
+
+void blk_rq_bio_prep(request_queue_t *q, struct request *rq, struct bio *bio)
+{
+	/* first three bits are identical in rq->flags and bio->bi_rw */
+	rq->flags |= (bio->bi_rw & 7);
+
+	rq->nr_phys_segments = bio_phys_segments(q, bio);
+	rq->nr_hw_segments = bio_hw_segments(q, bio);
+	rq->current_nr_sectors = bio_cur_sectors(bio);
+	rq->hard_cur_sectors = rq->current_nr_sectors;
+	rq->hard_nr_sectors = rq->nr_sectors = bio_sectors(bio);
+	rq->buffer = bio_data(bio);
+
+	rq->bio = rq->biotail = bio;
+}
+
+EXPORT_SYMBOL(blk_rq_bio_prep);
+
+int kblockd_schedule_work(struct work_struct *work)
+{
+	return queue_work(kblockd_workqueue, work);
+}
+
+EXPORT_SYMBOL(kblockd_schedule_work);
+
+void kblockd_flush(void)
+{
+	flush_workqueue(kblockd_workqueue);
+}
+EXPORT_SYMBOL(kblockd_flush);
+
+int __init blk_dev_init(void)
+{
+	kblockd_workqueue = create_workqueue("kblockd");
+	if (!kblockd_workqueue)
+		panic("Failed to create kblockd\n");
+
+	request_cachep = kmem_cache_create("blkdev_requests",
+			sizeof(struct request), 0, SLAB_PANIC, NULL, NULL);
+
+	requestq_cachep = kmem_cache_create("blkdev_queue",
+			sizeof(request_queue_t), 0, SLAB_PANIC, NULL, NULL);
+
+	iocontext_cachep = kmem_cache_create("blkdev_ioc",
+			sizeof(struct io_context), 0, SLAB_PANIC, NULL, NULL);
+
+	blk_max_low_pfn = max_low_pfn;
+	blk_max_pfn = max_pfn;
+
+	return 0;
+}
+
+/*
+ * IO Context helper functions
+ */
+void put_io_context(struct io_context *ioc)
+{
+	if (ioc == NULL)
+		return;
+
+	BUG_ON(atomic_read(&ioc->refcount) == 0);
+
+	if (atomic_dec_and_test(&ioc->refcount)) {
+		if (ioc->aic && ioc->aic->dtor)
+			ioc->aic->dtor(ioc->aic);
+		if (ioc->cic && ioc->cic->dtor)
+			ioc->cic->dtor(ioc->cic);
+
+		kmem_cache_free(iocontext_cachep, ioc);
+	}
+}
+EXPORT_SYMBOL(put_io_context);
+
+/* Called by the exitting task */
+void exit_io_context(void)
+{
+	unsigned long flags;
+	struct io_context *ioc;
+
+	local_irq_save(flags);
+	task_lock(current);
+	ioc = current->io_context;
+	current->io_context = NULL;
+	ioc->task = NULL;
+	task_unlock(current);
+	local_irq_restore(flags);
+
+	if (ioc->aic && ioc->aic->exit)
+		ioc->aic->exit(ioc->aic);
+	if (ioc->cic && ioc->cic->exit)
+		ioc->cic->exit(ioc->cic);
+
+	put_io_context(ioc);
+}
+
+/*
+ * If the current task has no IO context then create one and initialise it.
+ * Otherwise, return its existing IO context.
+ *
+ * This returned IO context doesn't have a specifically elevated refcount,
+ * but since the current task itself holds a reference, the context can be
+ * used in general code, so long as it stays within `current` context.
+ */
+struct io_context *current_io_context(gfp_t gfp_flags)
+{
+	struct task_struct *tsk = current;
+	struct io_context *ret;
+
+	ret = tsk->io_context;
+	if (likely(ret))
+		return ret;
+
+	ret = kmem_cache_alloc(iocontext_cachep, gfp_flags);
+	if (ret) {
+		atomic_set(&ret->refcount, 1);
+		ret->task = current;
+		ret->set_ioprio = NULL;
+		ret->last_waited = jiffies; /* doesn't matter... */
+		ret->nr_batch_requests = 0; /* because this is 0 */
+		ret->aic = NULL;
+		ret->cic = NULL;
+		tsk->io_context = ret;
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL(current_io_context);
+
+/*
+ * If the current task has no IO context then create one and initialise it.
+ * If it does have a context, take a ref on it.
+ *
+ * This is always called in the context of the task which submitted the I/O.
+ */
+struct io_context *get_io_context(gfp_t gfp_flags)
+{
+	struct io_context *ret;
+	ret = current_io_context(gfp_flags);
+	if (likely(ret))
+		atomic_inc(&ret->refcount);
+	return ret;
+}
+EXPORT_SYMBOL(get_io_context);
+
+void copy_io_context(struct io_context **pdst, struct io_context **psrc)
+{
+	struct io_context *src = *psrc;
+	struct io_context *dst = *pdst;
+
+	if (src) {
+		BUG_ON(atomic_read(&src->refcount) == 0);
+		atomic_inc(&src->refcount);
+		put_io_context(dst);
+		*pdst = src;
+	}
+}
+EXPORT_SYMBOL(copy_io_context);
+
+void swap_io_context(struct io_context **ioc1, struct io_context **ioc2)
+{
+	struct io_context *temp;
+	temp = *ioc1;
+	*ioc1 = *ioc2;
+	*ioc2 = temp;
+}
+EXPORT_SYMBOL(swap_io_context);
+
+/*
+ * sysfs parts below
+ */
+struct queue_sysfs_entry {
+	struct attribute attr;
+	ssize_t (*show)(struct request_queue *, char *);
+	ssize_t (*store)(struct request_queue *, const char *, size_t);
+};
+
+static ssize_t
+queue_var_show(unsigned int var, char *page)
+{
+	return sprintf(page, "%d\n", var);
+}
+
+static ssize_t
+queue_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 queue_requests_show(struct request_queue *q, char *page)
+{
+	return queue_var_show(q->nr_requests, (page));
+}
+
+static ssize_t
+queue_requests_store(struct request_queue *q, const char *page, size_t count)
+{
+	struct request_list *rl = &q->rq;
+
+	int ret = queue_var_store(&q->nr_requests, page, count);
+	if (q->nr_requests < BLKDEV_MIN_RQ)
+		q->nr_requests = BLKDEV_MIN_RQ;
+	blk_queue_congestion_threshold(q);
+
+	if (rl->count[READ] >= queue_congestion_on_threshold(q))
+		set_queue_congested(q, READ);
+	else if (rl->count[READ] < queue_congestion_off_threshold(q))
+		clear_queue_congested(q, READ);
+
+	if (rl->count[WRITE] >= queue_congestion_on_threshold(q))
+		set_queue_congested(q, WRITE);
+	else if (rl->count[WRITE] < queue_congestion_off_threshold(q))
+		clear_queue_congested(q, WRITE);
+
+	if (rl->count[READ] >= q->nr_requests) {
+		blk_set_queue_full(q, READ);
+	} else if (rl->count[READ]+1 <= q->nr_requests) {
+		blk_clear_queue_full(q, READ);
+		wake_up(&rl->wait[READ]);
+	}
+
+	if (rl->count[WRITE] >= q->nr_requests) {
+		blk_set_queue_full(q, WRITE);
+	} else if (rl->count[WRITE]+1 <= q->nr_requests) {
+		blk_clear_queue_full(q, WRITE);
+		wake_up(&rl->wait[WRITE]);
+	}
+	return ret;
+}
+
+static ssize_t queue_ra_show(struct request_queue *q, char *page)
+{
+	int ra_kb = q->backing_dev_info.ra_pages << (PAGE_CACHE_SHIFT - 10);
+
+	return queue_var_show(ra_kb, (page));
+}
+
+static ssize_t
+queue_ra_store(struct request_queue *q, const char *page, size_t count)
+{
+	unsigned long ra_kb;
+	ssize_t ret = queue_var_store(&ra_kb, page, count);
+
+	spin_lock_irq(q->queue_lock);
+	if (ra_kb > (q->max_sectors >> 1))
+		ra_kb = (q->max_sectors >> 1);
+
+	q->backing_dev_info.ra_pages = ra_kb >> (PAGE_CACHE_SHIFT - 10);
+	spin_unlock_irq(q->queue_lock);
+
+	return ret;
+}
+
+static ssize_t queue_max_sectors_show(struct request_queue *q, char *page)
+{
+	int max_sectors_kb = q->max_sectors >> 1;
+
+	return queue_var_show(max_sectors_kb, (page));
+}
+
+static ssize_t
+queue_max_sectors_store(struct request_queue *q, const char *page, size_t count)
+{
+	unsigned long max_sectors_kb,
+			max_hw_sectors_kb = q->max_hw_sectors >> 1,
+			page_kb = 1 << (PAGE_CACHE_SHIFT - 10);
+	ssize_t ret = queue_var_store(&max_sectors_kb, page, count);
+	int ra_kb;
+
+	if (max_sectors_kb > max_hw_sectors_kb || max_sectors_kb < page_kb)
+		return -EINVAL;
+	/*
+	 * Take the queue lock to update the readahead and max_sectors
+	 * values synchronously:
+	 */
+	spin_lock_irq(q->queue_lock);
+	/*
+	 * Trim readahead window as well, if necessary:
+	 */
+	ra_kb = q->backing_dev_info.ra_pages << (PAGE_CACHE_SHIFT - 10);
+	if (ra_kb > max_sectors_kb)
+		q->backing_dev_info.ra_pages =
+				max_sectors_kb >> (PAGE_CACHE_SHIFT - 10);
+
+	q->max_sectors = max_sectors_kb << 1;
+	spin_unlock_irq(q->queue_lock);
+
+	return ret;
+}
+
+static ssize_t queue_max_hw_sectors_show(struct request_queue *q, char *page)
+{
+	int max_hw_sectors_kb = q->max_hw_sectors >> 1;
+
+	return queue_var_show(max_hw_sectors_kb, (page));
+}
+
+
+static struct queue_sysfs_entry queue_requests_entry = {
+	.attr = {.name = "nr_requests", .mode = S_IRUGO | S_IWUSR },
+	.show = queue_requests_show,
+	.store = queue_requests_store,
+};
+
+static struct queue_sysfs_entry queue_ra_entry = {
+	.attr = {.name = "read_ahead_kb", .mode = S_IRUGO | S_IWUSR },
+	.show = queue_ra_show,
+	.store = queue_ra_store,
+};
+
+static struct queue_sysfs_entry queue_max_sectors_entry = {
+	.attr = {.name = "max_sectors_kb", .mode = S_IRUGO | S_IWUSR },
+	.show = queue_max_sectors_show,
+	.store = queue_max_sectors_store,
+};
+
+static struct queue_sysfs_entry queue_max_hw_sectors_entry = {
+	.attr = {.name = "max_hw_sectors_kb", .mode = S_IRUGO },
+	.show = queue_max_hw_sectors_show,
+};
+
+static struct queue_sysfs_entry queue_iosched_entry = {
+	.attr = {.name = "scheduler", .mode = S_IRUGO | S_IWUSR },
+	.show = elv_iosched_show,
+	.store = elv_iosched_store,
+};
+
+static struct attribute *default_attrs[] = {
+	&queue_requests_entry.attr,
+	&queue_ra_entry.attr,
+	&queue_max_hw_sectors_entry.attr,
+	&queue_max_sectors_entry.attr,
+	&queue_iosched_entry.attr,
+	NULL,
+};
+
+#define to_queue(atr) container_of((atr), struct queue_sysfs_entry, attr)
+
+static ssize_t
+queue_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
+{
+	struct queue_sysfs_entry *entry = to_queue(attr);
+	struct request_queue *q;
+
+	q = container_of(kobj, struct request_queue, kobj);
+	if (!entry->show)
+		return -EIO;
+
+	return entry->show(q, page);
+}
+
+static ssize_t
+queue_attr_store(struct kobject *kobj, struct attribute *attr,
+		    const char *page, size_t length)
+{
+	struct queue_sysfs_entry *entry = to_queue(attr);
+	struct request_queue *q;
+
+	q = container_of(kobj, struct request_queue, kobj);
+	if (!entry->store)
+		return -EIO;
+
+	return entry->store(q, page, length);
+}
+
+static struct sysfs_ops queue_sysfs_ops = {
+	.show	= queue_attr_show,
+	.store	= queue_attr_store,
+};
+
+static struct kobj_type queue_ktype = {
+	.sysfs_ops	= &queue_sysfs_ops,
+	.default_attrs	= default_attrs,
+};
+
+int blk_register_queue(struct gendisk *disk)
+{
+	int ret;
+
+	request_queue_t *q = disk->queue;
+
+	if (!q || !q->request_fn)
+		return -ENXIO;
+
+	q->kobj.parent = kobject_get(&disk->kobj);
+	if (!q->kobj.parent)
+		return -EBUSY;
+
+	snprintf(q->kobj.name, KOBJ_NAME_LEN, "%s", "queue");
+	q->kobj.ktype = &queue_ktype;
+
+	ret = kobject_register(&q->kobj);
+	if (ret < 0)
+		return ret;
+
+	ret = elv_register_queue(q);
+	if (ret) {
+		kobject_unregister(&q->kobj);
+		return ret;
+	}
+
+	return 0;
+}
+
+void blk_unregister_queue(struct gendisk *disk)
+{
+	request_queue_t *q = disk->queue;
+
+	if (q && q->request_fn) {
+		elv_unregister_queue(q);
+
+		kobject_unregister(&q->kobj);
+		kobject_put(&disk->kobj);
+	}
+}
diff --git a/block/noop-iosched.c b/block/noop-iosched.c
new file mode 100644
index 00000000000..e54f006e7e6
--- /dev/null
+++ b/block/noop-iosched.c
@@ -0,0 +1,46 @@
+/*
+ * elevator noop
+ */
+#include <linux/blkdev.h>
+#include <linux/elevator.h>
+#include <linux/bio.h>
+#include <linux/module.h>
+#include <linux/init.h>
+
+static void elevator_noop_add_request(request_queue_t *q, struct request *rq)
+{
+	rq->flags |= REQ_NOMERGE;
+	elv_dispatch_add_tail(q, rq);
+}
+
+static int elevator_noop_dispatch(request_queue_t *q, int force)
+{
+	return 0;
+}
+
+static struct elevator_type elevator_noop = {
+	.ops = {
+		.elevator_dispatch_fn		= elevator_noop_dispatch,
+		.elevator_add_req_fn		= elevator_noop_add_request,
+	},
+	.elevator_name = "noop",
+	.elevator_owner = THIS_MODULE,
+};
+
+static int __init noop_init(void)
+{
+	return elv_register(&elevator_noop);
+}
+
+static void __exit noop_exit(void)
+{
+	elv_unregister(&elevator_noop);
+}
+
+module_init(noop_init);
+module_exit(noop_exit);
+
+
+MODULE_AUTHOR("Jens Axboe");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("No-op IO scheduler");
diff --git a/block/scsi_ioctl.c b/block/scsi_ioctl.c
new file mode 100644
index 00000000000..382dea7b224
--- /dev/null
+++ b/block/scsi_ioctl.c
@@ -0,0 +1,589 @@
+/*
+ * Copyright (C) 2001 Jens Axboe <axboe@suse.de>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public Licens
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-
+ *
+ */
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/string.h>
+#include <linux/module.h>
+#include <linux/blkdev.h>
+#include <linux/completion.h>
+#include <linux/cdrom.h>
+#include <linux/slab.h>
+#include <linux/times.h>
+#include <asm/uaccess.h>
+
+#include <scsi/scsi.h>
+#include <scsi/scsi_ioctl.h>
+#include <scsi/scsi_cmnd.h>
+
+/* Command group 3 is reserved and should never be used.  */
+const unsigned char scsi_command_size[8] =
+{
+	6, 10, 10, 12,
+	16, 12, 10, 10
+};
+
+EXPORT_SYMBOL(scsi_command_size);
+
+#define BLK_DEFAULT_TIMEOUT	(60 * HZ)
+
+#include <scsi/sg.h>
+
+static int sg_get_version(int __user *p)
+{
+	static int sg_version_num = 30527;
+	return put_user(sg_version_num, p);
+}
+
+static int scsi_get_idlun(request_queue_t *q, int __user *p)
+{
+	return put_user(0, p);
+}
+
+static int scsi_get_bus(request_queue_t *q, int __user *p)
+{
+	return put_user(0, p);
+}
+
+static int sg_get_timeout(request_queue_t *q)
+{
+	return q->sg_timeout / (HZ / USER_HZ);
+}
+
+static int sg_set_timeout(request_queue_t *q, int __user *p)
+{
+	int timeout, err = get_user(timeout, p);
+
+	if (!err)
+		q->sg_timeout = timeout * (HZ / USER_HZ);
+
+	return err;
+}
+
+static int sg_get_reserved_size(request_queue_t *q, int __user *p)
+{
+	return put_user(q->sg_reserved_size, p);
+}
+
+static int sg_set_reserved_size(request_queue_t *q, int __user *p)
+{
+	int size, err = get_user(size, p);
+
+	if (err)
+		return err;
+
+	if (size < 0)
+		return -EINVAL;
+	if (size > (q->max_sectors << 9))
+		size = q->max_sectors << 9;
+
+	q->sg_reserved_size = size;
+	return 0;
+}
+
+/*
+ * will always return that we are ATAPI even for a real SCSI drive, I'm not
+ * so sure this is worth doing anything about (why would you care??)
+ */
+static int sg_emulated_host(request_queue_t *q, int __user *p)
+{
+	return put_user(1, p);
+}
+
+#define CMD_READ_SAFE	0x01
+#define CMD_WRITE_SAFE	0x02
+#define CMD_WARNED	0x04
+#define safe_for_read(cmd)	[cmd] = CMD_READ_SAFE
+#define safe_for_write(cmd)	[cmd] = CMD_WRITE_SAFE
+
+static int verify_command(struct file *file, unsigned char *cmd)
+{
+	static unsigned char cmd_type[256] = {
+
+		/* Basic read-only commands */
+		safe_for_read(TEST_UNIT_READY),
+		safe_for_read(REQUEST_SENSE),
+		safe_for_read(READ_6),
+		safe_for_read(READ_10),
+		safe_for_read(READ_12),
+		safe_for_read(READ_16),
+		safe_for_read(READ_BUFFER),
+		safe_for_read(READ_DEFECT_DATA),
+		safe_for_read(READ_LONG),
+		safe_for_read(INQUIRY),
+		safe_for_read(MODE_SENSE),
+		safe_for_read(MODE_SENSE_10),
+		safe_for_read(LOG_SENSE),
+		safe_for_read(START_STOP),
+		safe_for_read(GPCMD_VERIFY_10),
+		safe_for_read(VERIFY_16),
+
+		/* Audio CD commands */
+		safe_for_read(GPCMD_PLAY_CD),
+		safe_for_read(GPCMD_PLAY_AUDIO_10),
+		safe_for_read(GPCMD_PLAY_AUDIO_MSF),
+		safe_for_read(GPCMD_PLAY_AUDIO_TI),
+		safe_for_read(GPCMD_PAUSE_RESUME),
+
+		/* CD/DVD data reading */
+		safe_for_read(GPCMD_READ_BUFFER_CAPACITY),
+		safe_for_read(GPCMD_READ_CD),
+		safe_for_read(GPCMD_READ_CD_MSF),
+		safe_for_read(GPCMD_READ_DISC_INFO),
+		safe_for_read(GPCMD_READ_CDVD_CAPACITY),
+		safe_for_read(GPCMD_READ_DVD_STRUCTURE),
+		safe_for_read(GPCMD_READ_HEADER),
+		safe_for_read(GPCMD_READ_TRACK_RZONE_INFO),
+		safe_for_read(GPCMD_READ_SUBCHANNEL),
+		safe_for_read(GPCMD_READ_TOC_PMA_ATIP),
+		safe_for_read(GPCMD_REPORT_KEY),
+		safe_for_read(GPCMD_SCAN),
+		safe_for_read(GPCMD_GET_CONFIGURATION),
+		safe_for_read(GPCMD_READ_FORMAT_CAPACITIES),
+		safe_for_read(GPCMD_GET_EVENT_STATUS_NOTIFICATION),
+		safe_for_read(GPCMD_GET_PERFORMANCE),
+		safe_for_read(GPCMD_SEEK),
+		safe_for_read(GPCMD_STOP_PLAY_SCAN),
+
+		/* Basic writing commands */
+		safe_for_write(WRITE_6),
+		safe_for_write(WRITE_10),
+		safe_for_write(WRITE_VERIFY),
+		safe_for_write(WRITE_12),
+		safe_for_write(WRITE_VERIFY_12),
+		safe_for_write(WRITE_16),
+		safe_for_write(WRITE_LONG),
+		safe_for_write(WRITE_LONG_2),
+		safe_for_write(ERASE),
+		safe_for_write(GPCMD_MODE_SELECT_10),
+		safe_for_write(MODE_SELECT),
+		safe_for_write(LOG_SELECT),
+		safe_for_write(GPCMD_BLANK),
+		safe_for_write(GPCMD_CLOSE_TRACK),
+		safe_for_write(GPCMD_FLUSH_CACHE),
+		safe_for_write(GPCMD_FORMAT_UNIT),
+		safe_for_write(GPCMD_REPAIR_RZONE_TRACK),
+		safe_for_write(GPCMD_RESERVE_RZONE_TRACK),
+		safe_for_write(GPCMD_SEND_DVD_STRUCTURE),
+		safe_for_write(GPCMD_SEND_EVENT),
+		safe_for_write(GPCMD_SEND_KEY),
+		safe_for_write(GPCMD_SEND_OPC),
+		safe_for_write(GPCMD_SEND_CUE_SHEET),
+		safe_for_write(GPCMD_SET_SPEED),
+		safe_for_write(GPCMD_PREVENT_ALLOW_MEDIUM_REMOVAL),
+		safe_for_write(GPCMD_LOAD_UNLOAD),
+		safe_for_write(GPCMD_SET_STREAMING),
+	};
+	unsigned char type = cmd_type[cmd[0]];
+
+	/* Anybody who can open the device can do a read-safe command */
+	if (type & CMD_READ_SAFE)
+		return 0;
+
+	/* Write-safe commands just require a writable open.. */
+	if (type & CMD_WRITE_SAFE) {
+		if (file->f_mode & FMODE_WRITE)
+			return 0;
+	}
+
+	/* And root can do any command.. */
+	if (capable(CAP_SYS_RAWIO))
+		return 0;
+
+	if (!type) {
+		cmd_type[cmd[0]] = CMD_WARNED;
+		printk(KERN_WARNING "scsi: unknown opcode 0x%02x\n", cmd[0]);
+	}
+
+	/* Otherwise fail it with an "Operation not permitted" */
+	return -EPERM;
+}
+
+static int sg_io(struct file *file, request_queue_t *q,
+		struct gendisk *bd_disk, struct sg_io_hdr *hdr)
+{
+	unsigned long start_time;
+	int writing = 0, ret = 0;
+	struct request *rq;
+	struct bio *bio;
+	char sense[SCSI_SENSE_BUFFERSIZE];
+	unsigned char cmd[BLK_MAX_CDB];
+
+	if (hdr->interface_id != 'S')
+		return -EINVAL;
+	if (hdr->cmd_len > BLK_MAX_CDB)
+		return -EINVAL;
+	if (copy_from_user(cmd, hdr->cmdp, hdr->cmd_len))
+		return -EFAULT;
+	if (verify_command(file, cmd))
+		return -EPERM;
+
+	if (hdr->dxfer_len > (q->max_sectors << 9))
+		return -EIO;
+
+	if (hdr->dxfer_len)
+		switch (hdr->dxfer_direction) {
+		default:
+			return -EINVAL;
+		case SG_DXFER_TO_FROM_DEV:
+		case SG_DXFER_TO_DEV:
+			writing = 1;
+			break;
+		case SG_DXFER_FROM_DEV:
+			break;
+		}
+
+	rq = blk_get_request(q, writing ? WRITE : READ, GFP_KERNEL);
+	if (!rq)
+		return -ENOMEM;
+
+	if (hdr->iovec_count) {
+		const int size = sizeof(struct sg_iovec) * hdr->iovec_count;
+		struct sg_iovec *iov;
+
+		iov = kmalloc(size, GFP_KERNEL);
+		if (!iov) {
+			ret = -ENOMEM;
+			goto out;
+		}
+
+		if (copy_from_user(iov, hdr->dxferp, size)) {
+			kfree(iov);
+			ret = -EFAULT;
+			goto out;
+		}
+
+		ret = blk_rq_map_user_iov(q, rq, iov, hdr->iovec_count);
+		kfree(iov);
+	} else if (hdr->dxfer_len)
+		ret = blk_rq_map_user(q, rq, hdr->dxferp, hdr->dxfer_len);
+
+	if (ret)
+		goto out;
+
+	/*
+	 * fill in request structure
+	 */
+	rq->cmd_len = hdr->cmd_len;
+	memcpy(rq->cmd, cmd, hdr->cmd_len);
+	if (sizeof(rq->cmd) != hdr->cmd_len)
+		memset(rq->cmd + hdr->cmd_len, 0, sizeof(rq->cmd) - hdr->cmd_len);
+
+	memset(sense, 0, sizeof(sense));
+	rq->sense = sense;
+	rq->sense_len = 0;
+
+	rq->flags |= REQ_BLOCK_PC;
+	bio = rq->bio;
+
+	/*
+	 * bounce this after holding a reference to the original bio, it's
+	 * needed for proper unmapping
+	 */
+	if (rq->bio)
+		blk_queue_bounce(q, &rq->bio);
+
+	rq->timeout = (hdr->timeout * HZ) / 1000;
+	if (!rq->timeout)
+		rq->timeout = q->sg_timeout;
+	if (!rq->timeout)
+		rq->timeout = BLK_DEFAULT_TIMEOUT;
+
+	start_time = jiffies;
+
+	/* ignore return value. All information is passed back to caller
+	 * (if he doesn't check that is his problem).
+	 * N.B. a non-zero SCSI status is _not_ necessarily an error.
+	 */
+	blk_execute_rq(q, bd_disk, rq, 0);
+
+	/* write to all output members */
+	hdr->status = 0xff & rq->errors;
+	hdr->masked_status = status_byte(rq->errors);
+	hdr->msg_status = msg_byte(rq->errors);
+	hdr->host_status = host_byte(rq->errors);
+	hdr->driver_status = driver_byte(rq->errors);
+	hdr->info = 0;
+	if (hdr->masked_status || hdr->host_status || hdr->driver_status)
+		hdr->info |= SG_INFO_CHECK;
+	hdr->resid = rq->data_len;
+	hdr->duration = ((jiffies - start_time) * 1000) / HZ;
+	hdr->sb_len_wr = 0;
+
+	if (rq->sense_len && hdr->sbp) {
+		int len = min((unsigned int) hdr->mx_sb_len, rq->sense_len);
+
+		if (!copy_to_user(hdr->sbp, rq->sense, len))
+			hdr->sb_len_wr = len;
+	}
+
+	if (blk_rq_unmap_user(bio, hdr->dxfer_len))
+		ret = -EFAULT;
+
+	/* may not have succeeded, but output values written to control
+	 * structure (struct sg_io_hdr).  */
+out:
+	blk_put_request(rq);
+	return ret;
+}
+
+#define OMAX_SB_LEN 16          /* For backward compatibility */
+
+static int sg_scsi_ioctl(struct file *file, request_queue_t *q,
+			 struct gendisk *bd_disk, Scsi_Ioctl_Command __user *sic)
+{
+	struct request *rq;
+	int err;
+	unsigned int in_len, out_len, bytes, opcode, cmdlen;
+	char *buffer = NULL, sense[SCSI_SENSE_BUFFERSIZE];
+
+	/*
+	 * get in an out lengths, verify they don't exceed a page worth of data
+	 */
+	if (get_user(in_len, &sic->inlen))
+		return -EFAULT;
+	if (get_user(out_len, &sic->outlen))
+		return -EFAULT;
+	if (in_len > PAGE_SIZE || out_len > PAGE_SIZE)
+		return -EINVAL;
+	if (get_user(opcode, sic->data))
+		return -EFAULT;
+
+	bytes = max(in_len, out_len);
+	if (bytes) {
+		buffer = kmalloc(bytes, q->bounce_gfp | GFP_USER| __GFP_NOWARN);
+		if (!buffer)
+			return -ENOMEM;
+
+		memset(buffer, 0, bytes);
+	}
+
+	rq = blk_get_request(q, in_len ? WRITE : READ, __GFP_WAIT);
+
+	cmdlen = COMMAND_SIZE(opcode);
+
+	/*
+	 * get command and data to send to device, if any
+	 */
+	err = -EFAULT;
+	rq->cmd_len = cmdlen;
+	if (copy_from_user(rq->cmd, sic->data, cmdlen))
+		goto error;
+
+	if (copy_from_user(buffer, sic->data + cmdlen, in_len))
+		goto error;
+
+	err = verify_command(file, rq->cmd);
+	if (err)
+		goto error;
+
+	switch (opcode) {
+		case SEND_DIAGNOSTIC:
+		case FORMAT_UNIT:
+			rq->timeout = FORMAT_UNIT_TIMEOUT;
+			break;
+		case START_STOP:
+			rq->timeout = START_STOP_TIMEOUT;
+			break;
+		case MOVE_MEDIUM:
+			rq->timeout = MOVE_MEDIUM_TIMEOUT;
+			break;
+		case READ_ELEMENT_STATUS:
+			rq->timeout = READ_ELEMENT_STATUS_TIMEOUT;
+			break;
+		case READ_DEFECT_DATA:
+			rq->timeout = READ_DEFECT_DATA_TIMEOUT;
+			break;
+		default:
+			rq->timeout = BLK_DEFAULT_TIMEOUT;
+			break;
+	}
+
+	memset(sense, 0, sizeof(sense));
+	rq->sense = sense;
+	rq->sense_len = 0;
+
+	rq->data = buffer;
+	rq->data_len = bytes;
+	rq->flags |= REQ_BLOCK_PC;
+
+	blk_execute_rq(q, bd_disk, rq, 0);
+	err = rq->errors & 0xff;	/* only 8 bit SCSI status */
+	if (err) {
+		if (rq->sense_len && rq->sense) {
+			bytes = (OMAX_SB_LEN > rq->sense_len) ?
+				rq->sense_len : OMAX_SB_LEN;
+			if (copy_to_user(sic->data, rq->sense, bytes))
+				err = -EFAULT;
+		}
+	} else {
+		if (copy_to_user(sic->data, buffer, out_len))
+			err = -EFAULT;
+	}
+	
+error:
+	kfree(buffer);
+	blk_put_request(rq);
+	return err;
+}
+
+int scsi_cmd_ioctl(struct file *file, struct gendisk *bd_disk, unsigned int cmd, void __user *arg)
+{
+	request_queue_t *q;
+	struct request *rq;
+	int close = 0, err;
+
+	q = bd_disk->queue;
+	if (!q)
+		return -ENXIO;
+
+	if (blk_get_queue(q))
+		return -ENXIO;
+
+	switch (cmd) {
+		/*
+		 * new sgv3 interface
+		 */
+		case SG_GET_VERSION_NUM:
+			err = sg_get_version(arg);
+			break;
+		case SCSI_IOCTL_GET_IDLUN:
+			err = scsi_get_idlun(q, arg);
+			break;
+		case SCSI_IOCTL_GET_BUS_NUMBER:
+			err = scsi_get_bus(q, arg);
+			break;
+		case SG_SET_TIMEOUT:
+			err = sg_set_timeout(q, arg);
+			break;
+		case SG_GET_TIMEOUT:
+			err = sg_get_timeout(q);
+			break;
+		case SG_GET_RESERVED_SIZE:
+			err = sg_get_reserved_size(q, arg);
+			break;
+		case SG_SET_RESERVED_SIZE:
+			err = sg_set_reserved_size(q, arg);
+			break;
+		case SG_EMULATED_HOST:
+			err = sg_emulated_host(q, arg);
+			break;
+		case SG_IO: {
+			struct sg_io_hdr hdr;
+
+			err = -EFAULT;
+			if (copy_from_user(&hdr, arg, sizeof(hdr)))
+				break;
+			err = sg_io(file, q, bd_disk, &hdr);
+			if (err == -EFAULT)
+				break;
+
+			if (copy_to_user(arg, &hdr, sizeof(hdr)))
+				err = -EFAULT;
+			break;
+		}
+		case CDROM_SEND_PACKET: {
+			struct cdrom_generic_command cgc;
+			struct sg_io_hdr hdr;
+
+			err = -EFAULT;
+			if (copy_from_user(&cgc, arg, sizeof(cgc)))
+				break;
+			cgc.timeout = clock_t_to_jiffies(cgc.timeout);
+			memset(&hdr, 0, sizeof(hdr));
+			hdr.interface_id = 'S';
+			hdr.cmd_len = sizeof(cgc.cmd);
+			hdr.dxfer_len = cgc.buflen;
+			err = 0;
+			switch (cgc.data_direction) {
+				case CGC_DATA_UNKNOWN:
+					hdr.dxfer_direction = SG_DXFER_UNKNOWN;
+					break;
+				case CGC_DATA_WRITE:
+					hdr.dxfer_direction = SG_DXFER_TO_DEV;
+					break;
+				case CGC_DATA_READ:
+					hdr.dxfer_direction = SG_DXFER_FROM_DEV;
+					break;
+				case CGC_DATA_NONE:
+					hdr.dxfer_direction = SG_DXFER_NONE;
+					break;
+				default:
+					err = -EINVAL;
+			}
+			if (err)
+				break;
+
+			hdr.dxferp = cgc.buffer;
+			hdr.sbp = cgc.sense;
+			if (hdr.sbp)
+				hdr.mx_sb_len = sizeof(struct request_sense);
+			hdr.timeout = cgc.timeout;
+			hdr.cmdp = ((struct cdrom_generic_command __user*) arg)->cmd;
+			hdr.cmd_len = sizeof(cgc.cmd);
+
+			err = sg_io(file, q, bd_disk, &hdr);
+			if (err == -EFAULT)
+				break;
+
+			if (hdr.status)
+				err = -EIO;
+
+			cgc.stat = err;
+			cgc.buflen = hdr.resid;
+			if (copy_to_user(arg, &cgc, sizeof(cgc)))
+				err = -EFAULT;
+
+			break;
+		}
+
+		/*
+		 * old junk scsi send command ioctl
+		 */
+		case SCSI_IOCTL_SEND_COMMAND:
+			printk(KERN_WARNING "program %s is using a deprecated SCSI ioctl, please convert it to SG_IO\n", current->comm);
+			err = -EINVAL;
+			if (!arg)
+				break;
+
+			err = sg_scsi_ioctl(file, q, bd_disk, arg);
+			break;
+		case CDROMCLOSETRAY:
+			close = 1;
+		case CDROMEJECT:
+			rq = blk_get_request(q, WRITE, __GFP_WAIT);
+			rq->flags |= REQ_BLOCK_PC;
+			rq->data = NULL;
+			rq->data_len = 0;
+			rq->timeout = BLK_DEFAULT_TIMEOUT;
+			memset(rq->cmd, 0, sizeof(rq->cmd));
+			rq->cmd[0] = GPCMD_START_STOP_UNIT;
+			rq->cmd[4] = 0x02 + (close != 0);
+			rq->cmd_len = 6;
+			err = blk_execute_rq(q, bd_disk, rq, 0);
+			blk_put_request(rq);
+			break;
+		default:
+			err = -ENOTTY;
+	}
+
+	blk_put_queue(q);
+	return err;
+}
+
+EXPORT_SYMBOL(scsi_cmd_ioctl);