2 * linux/drivers/block/deadline-iosched.c
4 * Deadline i/o scheduler.
6 * Copyright (C) 2002 Jens Axboe <axboe@suse.de>
8 #include <linux/kernel.h>
10 #include <linux/blkdev.h>
11 #include <linux/elevator.h>
12 #include <linux/bio.h>
13 #include <linux/config.h>
14 #include <linux/module.h>
15 #include <linux/slab.h>
16 #include <linux/init.h>
17 #include <linux/compiler.h>
18 #include <linux/hash.h>
19 #include <linux/rbtree.h>
22 * See Documentation/block/deadline-iosched.txt
24 static int read_expire = HZ / 2; /* max time before a read is submitted. */
25 static int write_expire = 5 * HZ; /* ditto for writes, these limits are SOFT! */
26 static int writes_starved = 2; /* max times reads can starve a write */
27 static int fifo_batch = 16; /* # of sequential requests treated as one
28 by the above parameters. For throughput. */
30 static const int deadline_hash_shift = 5;
31 #define DL_HASH_BLOCK(sec) ((sec) >> 3)
32 #define DL_HASH_FN(sec) (hash_long(DL_HASH_BLOCK((sec)), deadline_hash_shift))
33 #define DL_HASH_ENTRIES (1 << deadline_hash_shift)
34 #define rq_hash_key(rq) ((rq)->sector + (rq)->nr_sectors)
35 #define list_entry_hash(ptr) list_entry((ptr), struct deadline_rq, hash)
36 #define ON_HASH(drq) (drq)->on_hash
38 struct deadline_data {
44 * requests (deadline_rq s) are present on both sort_list and fifo_list
46 struct rb_root sort_list[2];
47 struct list_head fifo_list[2];
50 * next in sort order. read, write or both are NULL
52 struct deadline_rq *next_drq[2];
53 struct list_head *dispatch; /* driver dispatch queue */
54 struct list_head *hash; /* request hash */
55 unsigned int batching; /* number of sequential requests made */
56 sector_t last_sector; /* head position */
57 unsigned int starved; /* times reads have starved writes */
60 * settings that change how the i/o scheduler behaves
75 * rbtree index, key is the starting offset
77 struct rb_node rb_node;
80 struct request *request;
83 * request hash, key is the ending offset (for back merge lookup)
85 struct list_head hash;
91 struct list_head fifo;
92 unsigned long expires;
95 static void deadline_move_request(struct deadline_data *dd, struct deadline_rq *drq);
97 static kmem_cache_t *drq_pool;
99 #define RQ_DATA(rq) ((struct deadline_rq *) (rq)->elevator_private)
102 * the back merge hash support functions
104 static inline void __deadline_del_drq_hash(struct deadline_rq *drq)
107 list_del_init(&drq->hash);
110 static inline void deadline_del_drq_hash(struct deadline_rq *drq)
113 __deadline_del_drq_hash(drq);
117 deadline_remove_merge_hints(request_queue_t *q, struct deadline_rq *drq)
119 deadline_del_drq_hash(drq);
121 if (q->last_merge == drq->request)
122 q->last_merge = NULL;
126 deadline_add_drq_hash(struct deadline_data *dd, struct deadline_rq *drq)
128 struct request *rq = drq->request;
130 BUG_ON(ON_HASH(drq));
133 list_add(&drq->hash, &dd->hash[DL_HASH_FN(rq_hash_key(rq))]);
137 * move hot entry to front of chain
140 deadline_hot_drq_hash(struct deadline_data *dd, struct deadline_rq *drq)
142 struct request *rq = drq->request;
143 struct list_head *head = &dd->hash[DL_HASH_FN(rq_hash_key(rq))];
145 if (ON_HASH(drq) && drq->hash.prev != head) {
146 list_del(&drq->hash);
147 list_add(&drq->hash, head);
151 static struct request *
152 deadline_find_drq_hash(struct deadline_data *dd, sector_t offset)
154 struct list_head *hash_list = &dd->hash[DL_HASH_FN(offset)];
155 struct list_head *entry, *next = hash_list->next;
157 while ((entry = next) != hash_list) {
158 struct deadline_rq *drq = list_entry_hash(entry);
159 struct request *__rq = drq->request;
163 BUG_ON(!ON_HASH(drq));
165 if (!rq_mergeable(__rq)) {
166 __deadline_del_drq_hash(drq);
170 if (rq_hash_key(__rq) == offset)
178 * rb tree support functions
181 #define RB_EMPTY(root) ((root)->rb_node == NULL)
182 #define ON_RB(node) ((node)->rb_color != RB_NONE)
183 #define RB_CLEAR(node) ((node)->rb_color = RB_NONE)
184 #define rb_entry_drq(node) rb_entry((node), struct deadline_rq, rb_node)
185 #define DRQ_RB_ROOT(dd, drq) (&(dd)->sort_list[rq_data_dir((drq)->request)])
186 #define rq_rb_key(rq) (rq)->sector
188 static struct deadline_rq *
189 __deadline_add_drq_rb(struct deadline_data *dd, struct deadline_rq *drq)
191 struct rb_node **p = &DRQ_RB_ROOT(dd, drq)->rb_node;
192 struct rb_node *parent = NULL;
193 struct deadline_rq *__drq;
197 __drq = rb_entry_drq(parent);
199 if (drq->rb_key < __drq->rb_key)
201 else if (drq->rb_key > __drq->rb_key)
207 rb_link_node(&drq->rb_node, parent, p);
212 deadline_add_drq_rb(struct deadline_data *dd, struct deadline_rq *drq)
214 struct deadline_rq *__alias;
216 drq->rb_key = rq_rb_key(drq->request);
219 __alias = __deadline_add_drq_rb(dd, drq);
221 rb_insert_color(&drq->rb_node, DRQ_RB_ROOT(dd, drq));
225 deadline_move_request(dd, __alias);
230 deadline_del_drq_rb(struct deadline_data *dd, struct deadline_rq *drq)
232 const int data_dir = rq_data_dir(drq->request);
234 if (dd->next_drq[data_dir] == drq) {
235 struct rb_node *rbnext = rb_next(&drq->rb_node);
237 dd->next_drq[data_dir] = NULL;
239 dd->next_drq[data_dir] = rb_entry_drq(rbnext);
242 if (ON_RB(&drq->rb_node)) {
243 rb_erase(&drq->rb_node, DRQ_RB_ROOT(dd, drq));
244 RB_CLEAR(&drq->rb_node);
248 static struct request *
249 deadline_find_drq_rb(struct deadline_data *dd, sector_t sector, int data_dir)
251 struct rb_node *n = dd->sort_list[data_dir].rb_node;
252 struct deadline_rq *drq;
255 drq = rb_entry_drq(n);
257 if (sector < drq->rb_key)
259 else if (sector > drq->rb_key)
269 * deadline_find_first_drq finds the first (lowest sector numbered) request
270 * for the specified data_dir. Used to sweep back to the start of the disk
271 * (1-way elevator) after we process the last (highest sector) request.
273 static struct deadline_rq *
274 deadline_find_first_drq(struct deadline_data *dd, int data_dir)
276 struct rb_node *n = dd->sort_list[data_dir].rb_node;
279 if (n->rb_left == NULL)
280 return rb_entry_drq(n);
287 * add drq to rbtree and fifo
290 deadline_add_request(struct request_queue *q, struct request *rq)
292 struct deadline_data *dd = q->elevator->elevator_data;
293 struct deadline_rq *drq = RQ_DATA(rq);
295 const int data_dir = rq_data_dir(drq->request);
297 deadline_add_drq_rb(dd, drq);
299 * set expire time (only used for reads) and add to fifo list
301 drq->expires = jiffies + dd->fifo_expire[data_dir];
302 list_add_tail(&drq->fifo, &dd->fifo_list[data_dir]);
304 if (rq_mergeable(rq)) {
305 deadline_add_drq_hash(dd, drq);
313 * remove rq from rbtree, fifo, and hash
315 static void deadline_remove_request(request_queue_t *q, struct request *rq)
317 struct deadline_rq *drq = RQ_DATA(rq);
320 struct deadline_data *dd = q->elevator->elevator_data;
322 list_del_init(&drq->fifo);
323 deadline_remove_merge_hints(q, drq);
324 deadline_del_drq_rb(dd, drq);
329 deadline_merge(request_queue_t *q, struct request **req, struct bio *bio)
331 struct deadline_data *dd = q->elevator->elevator_data;
332 struct request *__rq;
336 * try last_merge to avoid going to hash
338 ret = elv_try_last_merge(q, bio);
339 if (ret != ELEVATOR_NO_MERGE) {
340 __rq = q->last_merge;
345 * see if the merge hash can satisfy a back merge
347 __rq = deadline_find_drq_hash(dd, bio->bi_sector);
349 BUG_ON(__rq->sector + __rq->nr_sectors != bio->bi_sector);
351 if (elv_rq_merge_ok(__rq, bio)) {
352 ret = ELEVATOR_BACK_MERGE;
358 * check for front merge
360 if (dd->front_merges) {
361 sector_t rb_key = bio->bi_sector + bio_sectors(bio);
363 __rq = deadline_find_drq_rb(dd, rb_key, bio_data_dir(bio));
365 BUG_ON(rb_key != rq_rb_key(__rq));
367 if (elv_rq_merge_ok(__rq, bio)) {
368 ret = ELEVATOR_FRONT_MERGE;
374 return ELEVATOR_NO_MERGE;
376 q->last_merge = __rq;
379 deadline_hot_drq_hash(dd, RQ_DATA(__rq));
384 static void deadline_merged_request(request_queue_t *q, struct request *req)
386 struct deadline_data *dd = q->elevator->elevator_data;
387 struct deadline_rq *drq = RQ_DATA(req);
390 * hash always needs to be repositioned, key is end sector
392 deadline_del_drq_hash(drq);
393 deadline_add_drq_hash(dd, drq);
396 * if the merge was a front merge, we need to reposition request
398 if (rq_rb_key(req) != drq->rb_key) {
399 deadline_del_drq_rb(dd, drq);
400 deadline_add_drq_rb(dd, drq);
407 deadline_merged_requests(request_queue_t *q, struct request *req,
408 struct request *next)
410 struct deadline_data *dd = q->elevator->elevator_data;
411 struct deadline_rq *drq = RQ_DATA(req);
412 struct deadline_rq *dnext = RQ_DATA(next);
418 * reposition drq (this is the merged request) in hash, and in rbtree
419 * in case of a front merge
421 deadline_del_drq_hash(drq);
422 deadline_add_drq_hash(dd, drq);
424 if (rq_rb_key(req) != drq->rb_key) {
425 deadline_del_drq_rb(dd, drq);
426 deadline_add_drq_rb(dd, drq);
430 * if dnext expires before drq, assign its expire time to drq
431 * and move into dnext position (dnext will be deleted) in fifo
433 if (!list_empty(&drq->fifo) && !list_empty(&dnext->fifo)) {
434 if (time_before(dnext->expires, drq->expires)) {
435 list_move(&drq->fifo, &dnext->fifo);
436 drq->expires = dnext->expires;
441 * kill knowledge of next, this one is a goner
443 deadline_remove_request(q, next);
447 * move request from sort list to dispatch queue.
450 deadline_move_to_dispatch(struct deadline_data *dd, struct deadline_rq *drq)
452 request_queue_t *q = drq->request->q;
454 deadline_remove_request(q, drq->request);
455 list_add_tail(&drq->request->queuelist, dd->dispatch);
459 * move an entry to dispatch queue
462 deadline_move_request(struct deadline_data *dd, struct deadline_rq *drq)
464 const int data_dir = rq_data_dir(drq->request);
465 struct rb_node *rbnext = rb_next(&drq->rb_node);
467 dd->next_drq[READ] = NULL;
468 dd->next_drq[WRITE] = NULL;
471 dd->next_drq[data_dir] = rb_entry_drq(rbnext);
473 dd->last_sector = drq->request->sector + drq->request->nr_sectors;
476 * take it off the sort and fifo list, move
479 deadline_move_to_dispatch(dd, drq);
482 #define list_entry_fifo(ptr) list_entry((ptr), struct deadline_rq, fifo)
485 * deadline_check_fifo returns 0 if there are no expired reads on the fifo,
486 * 1 otherwise. Requires !list_empty(&dd->fifo_list[data_dir])
488 static inline int deadline_check_fifo(struct deadline_data *dd, int ddir)
490 struct deadline_rq *drq = list_entry_fifo(dd->fifo_list[ddir].next);
495 if (time_after(jiffies, drq->expires))
502 * deadline_dispatch_requests selects the best request according to
503 * read/write expire, fifo_batch, etc
505 static int deadline_dispatch_requests(struct deadline_data *dd)
507 const int reads = !list_empty(&dd->fifo_list[READ]);
508 const int writes = !list_empty(&dd->fifo_list[WRITE]);
509 struct deadline_rq *drq;
513 * batches are currently reads XOR writes
515 drq = dd->next_drq[WRITE] ? : dd->next_drq[READ];
518 /* we have a "next request" */
520 if (dd->last_sector != drq->request->sector)
521 /* end the batch on a non sequential request */
522 dd->batching += dd->fifo_batch;
524 if (dd->batching < dd->fifo_batch)
525 /* we are still entitled to batch */
526 goto dispatch_request;
530 * at this point we are not running a batch. select the appropriate
531 * data direction (read / write)
535 BUG_ON(RB_EMPTY(&dd->sort_list[READ]));
537 if (writes && (dd->starved++ >= dd->writes_starved))
538 goto dispatch_writes;
542 goto dispatch_find_request;
546 * there are either no reads or writes have been starved
551 BUG_ON(RB_EMPTY(&dd->sort_list[WRITE]));
557 goto dispatch_find_request;
562 dispatch_find_request:
564 * we are not running a batch, find best request for selected data_dir
566 if (deadline_check_fifo(dd, data_dir)) {
567 /* An expired request exists - satisfy it */
569 drq = list_entry_fifo(dd->fifo_list[data_dir].next);
571 } else if (dd->next_drq[data_dir]) {
573 * The last req was the same dir and we have a next request in
574 * sort order. No expired requests so continue on from here.
576 drq = dd->next_drq[data_dir];
579 * The last req was the other direction or we have run out of
580 * higher-sectored requests. Go back to the lowest sectored
581 * request (1 way elevator) and start a new batch.
584 drq = deadline_find_first_drq(dd, data_dir);
589 * drq is the selected appropriate request.
592 deadline_move_request(dd, drq);
597 static struct request *deadline_next_request(request_queue_t *q)
599 struct deadline_data *dd = q->elevator->elevator_data;
603 * if there are still requests on the dispatch queue, grab the first one
605 if (!list_empty(dd->dispatch)) {
607 rq = list_entry_rq(dd->dispatch->next);
611 if (deadline_dispatch_requests(dd))
618 deadline_insert_request(request_queue_t *q, struct request *rq, int where)
620 struct deadline_data *dd = q->elevator->elevator_data;
622 /* barriers must flush the reorder queue */
623 if (unlikely(rq->flags & (REQ_SOFTBARRIER | REQ_HARDBARRIER)
624 && where == ELEVATOR_INSERT_SORT))
625 where = ELEVATOR_INSERT_BACK;
628 case ELEVATOR_INSERT_BACK:
629 while (deadline_dispatch_requests(dd))
631 list_add_tail(&rq->queuelist, dd->dispatch);
633 case ELEVATOR_INSERT_FRONT:
634 list_add(&rq->queuelist, dd->dispatch);
636 case ELEVATOR_INSERT_SORT:
637 BUG_ON(!blk_fs_request(rq));
638 deadline_add_request(q, rq);
641 printk("%s: bad insert point %d\n", __FUNCTION__,where);
646 static int deadline_queue_empty(request_queue_t *q)
648 struct deadline_data *dd = q->elevator->elevator_data;
650 if (!list_empty(&dd->fifo_list[WRITE])
651 || !list_empty(&dd->fifo_list[READ])
652 || !list_empty(dd->dispatch))
658 static struct request *
659 deadline_former_request(request_queue_t *q, struct request *rq)
661 struct deadline_rq *drq = RQ_DATA(rq);
662 struct rb_node *rbprev = rb_prev(&drq->rb_node);
665 return rb_entry_drq(rbprev)->request;
670 static struct request *
671 deadline_latter_request(request_queue_t *q, struct request *rq)
673 struct deadline_rq *drq = RQ_DATA(rq);
674 struct rb_node *rbnext = rb_next(&drq->rb_node);
677 return rb_entry_drq(rbnext)->request;
682 static void deadline_exit_queue(elevator_t *e)
684 struct deadline_data *dd = e->elevator_data;
686 BUG_ON(!list_empty(&dd->fifo_list[READ]));
687 BUG_ON(!list_empty(&dd->fifo_list[WRITE]));
689 mempool_destroy(dd->drq_pool);
695 * initialize elevator private data (deadline_data), and alloc a drq for
696 * each request on the free lists
698 static int deadline_init_queue(request_queue_t *q, elevator_t *e)
700 struct deadline_data *dd;
706 dd = kmalloc_node(sizeof(*dd), GFP_KERNEL, q->node);
709 memset(dd, 0, sizeof(*dd));
711 dd->hash = kmalloc_node(sizeof(struct list_head)*DL_HASH_ENTRIES,
712 GFP_KERNEL, q->node);
718 dd->drq_pool = mempool_create_node(BLKDEV_MIN_RQ, mempool_alloc_slab,
719 mempool_free_slab, drq_pool, q->node);
726 for (i = 0; i < DL_HASH_ENTRIES; i++)
727 INIT_LIST_HEAD(&dd->hash[i]);
729 INIT_LIST_HEAD(&dd->fifo_list[READ]);
730 INIT_LIST_HEAD(&dd->fifo_list[WRITE]);
731 dd->sort_list[READ] = RB_ROOT;
732 dd->sort_list[WRITE] = RB_ROOT;
733 dd->dispatch = &q->queue_head;
734 dd->fifo_expire[READ] = read_expire;
735 dd->fifo_expire[WRITE] = write_expire;
736 dd->writes_starved = writes_starved;
737 dd->front_merges = 1;
738 dd->fifo_batch = fifo_batch;
739 e->elevator_data = dd;
743 static void deadline_put_request(request_queue_t *q, struct request *rq)
745 struct deadline_data *dd = q->elevator->elevator_data;
746 struct deadline_rq *drq = RQ_DATA(rq);
749 mempool_free(drq, dd->drq_pool);
750 rq->elevator_private = NULL;
755 deadline_set_request(request_queue_t *q, struct request *rq, struct bio *bio,
758 struct deadline_data *dd = q->elevator->elevator_data;
759 struct deadline_rq *drq;
761 drq = mempool_alloc(dd->drq_pool, gfp_mask);
763 memset(drq, 0, sizeof(*drq));
764 RB_CLEAR(&drq->rb_node);
767 INIT_LIST_HEAD(&drq->hash);
770 INIT_LIST_HEAD(&drq->fifo);
772 rq->elevator_private = drq;
782 struct deadline_fs_entry {
783 struct attribute attr;
784 ssize_t (*show)(struct deadline_data *, char *);
785 ssize_t (*store)(struct deadline_data *, const char *, size_t);
789 deadline_var_show(int var, char *page)
791 return sprintf(page, "%d\n", var);
795 deadline_var_store(int *var, const char *page, size_t count)
797 char *p = (char *) page;
799 *var = simple_strtol(p, &p, 10);
803 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
804 static ssize_t __FUNC(struct deadline_data *dd, char *page) \
806 int __data = __VAR; \
808 __data = jiffies_to_msecs(__data); \
809 return deadline_var_show(__data, (page)); \
811 SHOW_FUNCTION(deadline_readexpire_show, dd->fifo_expire[READ], 1);
812 SHOW_FUNCTION(deadline_writeexpire_show, dd->fifo_expire[WRITE], 1);
813 SHOW_FUNCTION(deadline_writesstarved_show, dd->writes_starved, 0);
814 SHOW_FUNCTION(deadline_frontmerges_show, dd->front_merges, 0);
815 SHOW_FUNCTION(deadline_fifobatch_show, dd->fifo_batch, 0);
818 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
819 static ssize_t __FUNC(struct deadline_data *dd, const char *page, size_t count) \
822 int ret = deadline_var_store(&__data, (page), count); \
823 if (__data < (MIN)) \
825 else if (__data > (MAX)) \
828 *(__PTR) = msecs_to_jiffies(__data); \
833 STORE_FUNCTION(deadline_readexpire_store, &dd->fifo_expire[READ], 0, INT_MAX, 1);
834 STORE_FUNCTION(deadline_writeexpire_store, &dd->fifo_expire[WRITE], 0, INT_MAX, 1);
835 STORE_FUNCTION(deadline_writesstarved_store, &dd->writes_starved, INT_MIN, INT_MAX, 0);
836 STORE_FUNCTION(deadline_frontmerges_store, &dd->front_merges, 0, 1, 0);
837 STORE_FUNCTION(deadline_fifobatch_store, &dd->fifo_batch, 0, INT_MAX, 0);
838 #undef STORE_FUNCTION
840 static struct deadline_fs_entry deadline_readexpire_entry = {
841 .attr = {.name = "read_expire", .mode = S_IRUGO | S_IWUSR },
842 .show = deadline_readexpire_show,
843 .store = deadline_readexpire_store,
845 static struct deadline_fs_entry deadline_writeexpire_entry = {
846 .attr = {.name = "write_expire", .mode = S_IRUGO | S_IWUSR },
847 .show = deadline_writeexpire_show,
848 .store = deadline_writeexpire_store,
850 static struct deadline_fs_entry deadline_writesstarved_entry = {
851 .attr = {.name = "writes_starved", .mode = S_IRUGO | S_IWUSR },
852 .show = deadline_writesstarved_show,
853 .store = deadline_writesstarved_store,
855 static struct deadline_fs_entry deadline_frontmerges_entry = {
856 .attr = {.name = "front_merges", .mode = S_IRUGO | S_IWUSR },
857 .show = deadline_frontmerges_show,
858 .store = deadline_frontmerges_store,
860 static struct deadline_fs_entry deadline_fifobatch_entry = {
861 .attr = {.name = "fifo_batch", .mode = S_IRUGO | S_IWUSR },
862 .show = deadline_fifobatch_show,
863 .store = deadline_fifobatch_store,
866 static struct attribute *default_attrs[] = {
867 &deadline_readexpire_entry.attr,
868 &deadline_writeexpire_entry.attr,
869 &deadline_writesstarved_entry.attr,
870 &deadline_frontmerges_entry.attr,
871 &deadline_fifobatch_entry.attr,
875 #define to_deadline(atr) container_of((atr), struct deadline_fs_entry, attr)
878 deadline_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
880 elevator_t *e = container_of(kobj, elevator_t, kobj);
881 struct deadline_fs_entry *entry = to_deadline(attr);
886 return entry->show(e->elevator_data, page);
890 deadline_attr_store(struct kobject *kobj, struct attribute *attr,
891 const char *page, size_t length)
893 elevator_t *e = container_of(kobj, elevator_t, kobj);
894 struct deadline_fs_entry *entry = to_deadline(attr);
899 return entry->store(e->elevator_data, page, length);
902 static struct sysfs_ops deadline_sysfs_ops = {
903 .show = deadline_attr_show,
904 .store = deadline_attr_store,
907 static struct kobj_type deadline_ktype = {
908 .sysfs_ops = &deadline_sysfs_ops,
909 .default_attrs = default_attrs,
912 static struct elevator_type iosched_deadline = {
914 .elevator_merge_fn = deadline_merge,
915 .elevator_merged_fn = deadline_merged_request,
916 .elevator_merge_req_fn = deadline_merged_requests,
917 .elevator_next_req_fn = deadline_next_request,
918 .elevator_add_req_fn = deadline_insert_request,
919 .elevator_remove_req_fn = deadline_remove_request,
920 .elevator_queue_empty_fn = deadline_queue_empty,
921 .elevator_former_req_fn = deadline_former_request,
922 .elevator_latter_req_fn = deadline_latter_request,
923 .elevator_set_req_fn = deadline_set_request,
924 .elevator_put_req_fn = deadline_put_request,
925 .elevator_init_fn = deadline_init_queue,
926 .elevator_exit_fn = deadline_exit_queue,
929 .elevator_ktype = &deadline_ktype,
930 .elevator_name = "deadline",
931 .elevator_owner = THIS_MODULE,
934 static int __init deadline_init(void)
938 drq_pool = kmem_cache_create("deadline_drq", sizeof(struct deadline_rq),
944 ret = elv_register(&iosched_deadline);
946 kmem_cache_destroy(drq_pool);
951 static void __exit deadline_exit(void)
953 kmem_cache_destroy(drq_pool);
954 elv_unregister(&iosched_deadline);
957 module_init(deadline_init);
958 module_exit(deadline_exit);
960 MODULE_AUTHOR("Jens Axboe");
961 MODULE_LICENSE("GPL");
962 MODULE_DESCRIPTION("deadline IO scheduler");