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

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

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

1 files changed, 0 insertions, 802 deletions

diff --git a/drivers/block/elevator.c b/drivers/block/elevator.c
deleted file mode 100644
index d4a49a3df829..000000000000
--- a/drivers/block/elevator.c
+++ /dev/null
@@ -1,802 +0,0 @@
-/*
- *  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);