blob: c644137d9cd643b0e3b80750333dc42e92d1e964 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07002 * Deadline i/o scheduler.
3 *
Jens Axboe0fe23472006-09-04 15:41:16 +02004 * Copyright (C) 2002 Jens Axboe <axboe@kernel.dk>
Linus Torvalds1da177e2005-04-16 15:20:36 -07005 */
6#include <linux/kernel.h>
7#include <linux/fs.h>
8#include <linux/blkdev.h>
9#include <linux/elevator.h>
10#include <linux/bio.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070011#include <linux/module.h>
12#include <linux/slab.h>
13#include <linux/init.h>
14#include <linux/compiler.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070015#include <linux/rbtree.h>
16
17/*
18 * See Documentation/block/deadline-iosched.txt
19 */
Arjan van de Ven64100092006-01-06 09:46:02 +010020static const int read_expire = HZ / 2; /* max time before a read is submitted. */
21static const int write_expire = 5 * HZ; /* ditto for writes, these limits are SOFT! */
22static const int writes_starved = 2; /* max times reads can starve a write */
23static const int fifo_batch = 16; /* # of sequential requests treated as one
Linus Torvalds1da177e2005-04-16 15:20:36 -070024 by the above parameters. For throughput. */
25
Linus Torvalds1da177e2005-04-16 15:20:36 -070026struct deadline_data {
27 /*
28 * run time data
29 */
30
31 /*
32 * requests (deadline_rq s) are present on both sort_list and fifo_list
33 */
34 struct rb_root sort_list[2];
35 struct list_head fifo_list[2];
Aaron Carroll4fb72f72008-08-14 18:17:14 +100036
Linus Torvalds1da177e2005-04-16 15:20:36 -070037 /*
38 * next in sort order. read, write or both are NULL
39 */
Jens Axboe8840faa2006-07-13 12:36:41 +020040 struct request *next_rq[2];
Linus Torvalds1da177e2005-04-16 15:20:36 -070041 unsigned int batching; /* number of sequential requests made */
42 sector_t last_sector; /* head position */
43 unsigned int starved; /* times reads have starved writes */
44
45 /*
46 * settings that change how the i/o scheduler behaves
47 */
48 int fifo_expire[2];
49 int fifo_batch;
50 int writes_starved;
51 int front_merges;
Linus Torvalds1da177e2005-04-16 15:20:36 -070052};
53
Jens Axboe8840faa2006-07-13 12:36:41 +020054static void deadline_move_request(struct deadline_data *, struct request *);
Linus Torvalds1da177e2005-04-16 15:20:36 -070055
Aaron Carroll4fb72f72008-08-14 18:17:14 +100056static inline struct rb_root *
57deadline_rb_root(struct deadline_data *dd, struct request *rq)
58{
59 return &dd->sort_list[rq_data_dir(rq)];
60}
Linus Torvalds1da177e2005-04-16 15:20:36 -070061
Aaron Carroll5d1a5362007-10-30 10:40:12 +010062/*
63 * get the request after `rq' in sector-sorted order
64 */
65static inline struct request *
66deadline_latter_request(struct request *rq)
67{
68 struct rb_node *node = rb_next(&rq->rb_node);
69
70 if (node)
71 return rb_entry_rq(node);
72
73 return NULL;
74}
75
Linus Torvalds1da177e2005-04-16 15:20:36 -070076static void
Jens Axboe8840faa2006-07-13 12:36:41 +020077deadline_add_rq_rb(struct deadline_data *dd, struct request *rq)
Linus Torvalds1da177e2005-04-16 15:20:36 -070078{
Aaron Carroll4fb72f72008-08-14 18:17:14 +100079 struct rb_root *root = deadline_rb_root(dd, rq);
Linus Torvalds1da177e2005-04-16 15:20:36 -070080
Jeff Moyer796d5112011-06-02 21:19:05 +020081 elv_rb_add(root, rq);
Linus Torvalds1da177e2005-04-16 15:20:36 -070082}
83
84static inline void
Jens Axboe8840faa2006-07-13 12:36:41 +020085deadline_del_rq_rb(struct deadline_data *dd, struct request *rq)
Linus Torvalds1da177e2005-04-16 15:20:36 -070086{
Jens Axboeb8aca352006-07-13 12:34:24 +020087 const int data_dir = rq_data_dir(rq);
Linus Torvalds1da177e2005-04-16 15:20:36 -070088
Aaron Carroll5d1a5362007-10-30 10:40:12 +010089 if (dd->next_rq[data_dir] == rq)
90 dd->next_rq[data_dir] = deadline_latter_request(rq);
Linus Torvalds1da177e2005-04-16 15:20:36 -070091
Aaron Carroll4fb72f72008-08-14 18:17:14 +100092 elv_rb_del(deadline_rb_root(dd, rq), rq);
Linus Torvalds1da177e2005-04-16 15:20:36 -070093}
94
95/*
Jens Axboe8840faa2006-07-13 12:36:41 +020096 * add rq to rbtree and fifo
Linus Torvalds1da177e2005-04-16 15:20:36 -070097 */
Jens Axboeb4878f22005-10-20 16:42:29 +020098static void
Linus Torvalds1da177e2005-04-16 15:20:36 -070099deadline_add_request(struct request_queue *q, struct request *rq)
100{
101 struct deadline_data *dd = q->elevator->elevator_data;
Jens Axboe8840faa2006-07-13 12:36:41 +0200102 const int data_dir = rq_data_dir(rq);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700103
Jens Axboe8840faa2006-07-13 12:36:41 +0200104 deadline_add_rq_rb(dd, rq);
Jens Axboe98170642006-07-28 09:23:08 +0200105
Linus Torvalds1da177e2005-04-16 15:20:36 -0700106 /*
Aaron Carroll4fb72f72008-08-14 18:17:14 +1000107 * set expire time and add to fifo list
Linus Torvalds1da177e2005-04-16 15:20:36 -0700108 */
Jens Axboe8840faa2006-07-13 12:36:41 +0200109 rq_set_fifo_time(rq, jiffies + dd->fifo_expire[data_dir]);
110 list_add_tail(&rq->queuelist, &dd->fifo_list[data_dir]);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700111}
112
113/*
Jens Axboe98170642006-07-28 09:23:08 +0200114 * remove rq from rbtree and fifo.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700115 */
Jens Axboe165125e2007-07-24 09:28:11 +0200116static void deadline_remove_request(struct request_queue *q, struct request *rq)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700117{
Jens Axboeb4878f22005-10-20 16:42:29 +0200118 struct deadline_data *dd = q->elevator->elevator_data;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700119
Jens Axboe8840faa2006-07-13 12:36:41 +0200120 rq_fifo_clear(rq);
121 deadline_del_rq_rb(dd, rq);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700122}
123
124static int
Jens Axboe165125e2007-07-24 09:28:11 +0200125deadline_merge(struct request_queue *q, struct request **req, struct bio *bio)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700126{
127 struct deadline_data *dd = q->elevator->elevator_data;
128 struct request *__rq;
129 int ret;
130
131 /*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700132 * check for front merge
133 */
134 if (dd->front_merges) {
Jens Axboeb8aca352006-07-13 12:34:24 +0200135 sector_t sector = bio->bi_sector + bio_sectors(bio);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700136
Jens Axboeb8aca352006-07-13 12:34:24 +0200137 __rq = elv_rb_find(&dd->sort_list[bio_data_dir(bio)], sector);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700138 if (__rq) {
Tejun Heo83096eb2009-05-07 22:24:39 +0900139 BUG_ON(sector != blk_rq_pos(__rq));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700140
141 if (elv_rq_merge_ok(__rq, bio)) {
142 ret = ELEVATOR_FRONT_MERGE;
143 goto out;
144 }
145 }
146 }
147
148 return ELEVATOR_NO_MERGE;
149out:
Linus Torvalds1da177e2005-04-16 15:20:36 -0700150 *req = __rq;
151 return ret;
152}
153
Jens Axboe165125e2007-07-24 09:28:11 +0200154static void deadline_merged_request(struct request_queue *q,
155 struct request *req, int type)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700156{
157 struct deadline_data *dd = q->elevator->elevator_data;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700158
159 /*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700160 * if the merge was a front merge, we need to reposition request
161 */
Jens Axboeb8aca352006-07-13 12:34:24 +0200162 if (type == ELEVATOR_FRONT_MERGE) {
Aaron Carroll4fb72f72008-08-14 18:17:14 +1000163 elv_rb_del(deadline_rb_root(dd, req), req);
Jens Axboe8840faa2006-07-13 12:36:41 +0200164 deadline_add_rq_rb(dd, req);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700165 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700166}
167
168static void
Jens Axboe165125e2007-07-24 09:28:11 +0200169deadline_merged_requests(struct request_queue *q, struct request *req,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700170 struct request *next)
171{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700172 /*
Jens Axboe8840faa2006-07-13 12:36:41 +0200173 * if next expires before rq, assign its expire time to rq
174 * and move into next position (next will be deleted) in fifo
Linus Torvalds1da177e2005-04-16 15:20:36 -0700175 */
Jens Axboe8840faa2006-07-13 12:36:41 +0200176 if (!list_empty(&req->queuelist) && !list_empty(&next->queuelist)) {
177 if (time_before(rq_fifo_time(next), rq_fifo_time(req))) {
178 list_move(&req->queuelist, &next->queuelist);
179 rq_set_fifo_time(req, rq_fifo_time(next));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700180 }
181 }
182
183 /*
184 * kill knowledge of next, this one is a goner
185 */
186 deadline_remove_request(q, next);
187}
188
189/*
190 * move request from sort list to dispatch queue.
191 */
192static inline void
Jens Axboe8840faa2006-07-13 12:36:41 +0200193deadline_move_to_dispatch(struct deadline_data *dd, struct request *rq)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700194{
Jens Axboe165125e2007-07-24 09:28:11 +0200195 struct request_queue *q = rq->q;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700196
Jens Axboe8840faa2006-07-13 12:36:41 +0200197 deadline_remove_request(q, rq);
198 elv_dispatch_add_tail(q, rq);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700199}
200
201/*
202 * move an entry to dispatch queue
203 */
204static void
Jens Axboe8840faa2006-07-13 12:36:41 +0200205deadline_move_request(struct deadline_data *dd, struct request *rq)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700206{
Jens Axboeb8aca352006-07-13 12:34:24 +0200207 const int data_dir = rq_data_dir(rq);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700208
Jens Axboe8840faa2006-07-13 12:36:41 +0200209 dd->next_rq[READ] = NULL;
210 dd->next_rq[WRITE] = NULL;
Aaron Carroll5d1a5362007-10-30 10:40:12 +0100211 dd->next_rq[data_dir] = deadline_latter_request(rq);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700212
Aaron Carroll4fb72f72008-08-14 18:17:14 +1000213 dd->last_sector = rq_end_sector(rq);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700214
215 /*
216 * take it off the sort and fifo list, move
217 * to dispatch queue
218 */
Jens Axboe8840faa2006-07-13 12:36:41 +0200219 deadline_move_to_dispatch(dd, rq);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700220}
221
Linus Torvalds1da177e2005-04-16 15:20:36 -0700222/*
Aaron Carroll4fb72f72008-08-14 18:17:14 +1000223 * deadline_check_fifo returns 0 if there are no expired requests on the fifo,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700224 * 1 otherwise. Requires !list_empty(&dd->fifo_list[data_dir])
225 */
226static inline int deadline_check_fifo(struct deadline_data *dd, int ddir)
227{
Jens Axboe8840faa2006-07-13 12:36:41 +0200228 struct request *rq = rq_entry_fifo(dd->fifo_list[ddir].next);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700229
230 /*
Jens Axboe8840faa2006-07-13 12:36:41 +0200231 * rq is expired!
Linus Torvalds1da177e2005-04-16 15:20:36 -0700232 */
Jens Axboe8840faa2006-07-13 12:36:41 +0200233 if (time_after(jiffies, rq_fifo_time(rq)))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700234 return 1;
235
236 return 0;
237}
238
239/*
240 * deadline_dispatch_requests selects the best request according to
241 * read/write expire, fifo_batch, etc
242 */
Jens Axboe165125e2007-07-24 09:28:11 +0200243static int deadline_dispatch_requests(struct request_queue *q, int force)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700244{
Jens Axboeb4878f22005-10-20 16:42:29 +0200245 struct deadline_data *dd = q->elevator->elevator_data;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700246 const int reads = !list_empty(&dd->fifo_list[READ]);
247 const int writes = !list_empty(&dd->fifo_list[WRITE]);
Jens Axboe8840faa2006-07-13 12:36:41 +0200248 struct request *rq;
Nikita Danilov4b0dc072005-09-06 15:17:20 -0700249 int data_dir;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700250
251 /*
252 * batches are currently reads XOR writes
253 */
Jens Axboe8840faa2006-07-13 12:36:41 +0200254 if (dd->next_rq[WRITE])
255 rq = dd->next_rq[WRITE];
Andrew Morton9d5c1e12005-09-09 13:02:12 -0700256 else
Jens Axboe8840faa2006-07-13 12:36:41 +0200257 rq = dd->next_rq[READ];
Linus Torvalds1da177e2005-04-16 15:20:36 -0700258
Aaron Carroll63de4282008-08-14 18:17:13 +1000259 if (rq && dd->batching < dd->fifo_batch)
260 /* we have a next request are still entitled to batch */
261 goto dispatch_request;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700262
263 /*
264 * at this point we are not running a batch. select the appropriate
265 * data direction (read / write)
266 */
267
268 if (reads) {
Jens Axboedd67d052006-06-21 09:36:18 +0200269 BUG_ON(RB_EMPTY_ROOT(&dd->sort_list[READ]));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700270
271 if (writes && (dd->starved++ >= dd->writes_starved))
272 goto dispatch_writes;
273
274 data_dir = READ;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700275
276 goto dispatch_find_request;
277 }
278
279 /*
280 * there are either no reads or writes have been starved
281 */
282
283 if (writes) {
284dispatch_writes:
Jens Axboedd67d052006-06-21 09:36:18 +0200285 BUG_ON(RB_EMPTY_ROOT(&dd->sort_list[WRITE]));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700286
287 dd->starved = 0;
288
289 data_dir = WRITE;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700290
291 goto dispatch_find_request;
292 }
293
294 return 0;
295
296dispatch_find_request:
297 /*
298 * we are not running a batch, find best request for selected data_dir
299 */
Aaron Carroll6f5d8aa2007-10-30 10:40:13 +0100300 if (deadline_check_fifo(dd, data_dir) || !dd->next_rq[data_dir]) {
301 /*
302 * A deadline has expired, the last request was in the other
303 * direction, or we have run out of higher-sectored requests.
304 * Start again from the request with the earliest expiry time.
305 */
Jens Axboe8840faa2006-07-13 12:36:41 +0200306 rq = rq_entry_fifo(dd->fifo_list[data_dir].next);
Aaron Carroll6f5d8aa2007-10-30 10:40:13 +0100307 } else {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700308 /*
309 * The last req was the same dir and we have a next request in
310 * sort order. No expired requests so continue on from here.
311 */
Jens Axboe8840faa2006-07-13 12:36:41 +0200312 rq = dd->next_rq[data_dir];
Linus Torvalds1da177e2005-04-16 15:20:36 -0700313 }
314
Aaron Carrolldfb3d722007-10-30 10:40:13 +0100315 dd->batching = 0;
316
Linus Torvalds1da177e2005-04-16 15:20:36 -0700317dispatch_request:
318 /*
Jens Axboe8840faa2006-07-13 12:36:41 +0200319 * rq is the selected appropriate request.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700320 */
321 dd->batching++;
Jens Axboe8840faa2006-07-13 12:36:41 +0200322 deadline_move_request(dd, rq);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700323
324 return 1;
325}
326
Jens Axboeb374d182008-10-31 10:05:07 +0100327static void deadline_exit_queue(struct elevator_queue *e)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700328{
329 struct deadline_data *dd = e->elevator_data;
330
331 BUG_ON(!list_empty(&dd->fifo_list[READ]));
332 BUG_ON(!list_empty(&dd->fifo_list[WRITE]));
333
Linus Torvalds1da177e2005-04-16 15:20:36 -0700334 kfree(dd);
335}
336
337/*
Jens Axboe8840faa2006-07-13 12:36:41 +0200338 * initialize elevator private data (deadline_data).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700339 */
Jens Axboe165125e2007-07-24 09:28:11 +0200340static void *deadline_init_queue(struct request_queue *q)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700341{
342 struct deadline_data *dd;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700343
Christoph Lameter94f60302007-07-17 04:03:29 -0700344 dd = kmalloc_node(sizeof(*dd), GFP_KERNEL | __GFP_ZERO, q->node);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700345 if (!dd)
Jens Axboebc1c1162006-06-08 08:49:06 +0200346 return NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700347
Linus Torvalds1da177e2005-04-16 15:20:36 -0700348 INIT_LIST_HEAD(&dd->fifo_list[READ]);
349 INIT_LIST_HEAD(&dd->fifo_list[WRITE]);
350 dd->sort_list[READ] = RB_ROOT;
351 dd->sort_list[WRITE] = RB_ROOT;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700352 dd->fifo_expire[READ] = read_expire;
353 dd->fifo_expire[WRITE] = write_expire;
354 dd->writes_starved = writes_starved;
355 dd->front_merges = 1;
356 dd->fifo_batch = fifo_batch;
Jens Axboebc1c1162006-06-08 08:49:06 +0200357 return dd;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700358}
359
Linus Torvalds1da177e2005-04-16 15:20:36 -0700360/*
361 * sysfs parts below
362 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700363
364static ssize_t
365deadline_var_show(int var, char *page)
366{
367 return sprintf(page, "%d\n", var);
368}
369
370static ssize_t
371deadline_var_store(int *var, const char *page, size_t count)
372{
373 char *p = (char *) page;
374
375 *var = simple_strtol(p, &p, 10);
376 return count;
377}
378
379#define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
Jens Axboeb374d182008-10-31 10:05:07 +0100380static ssize_t __FUNC(struct elevator_queue *e, char *page) \
Linus Torvalds1da177e2005-04-16 15:20:36 -0700381{ \
Al Viro3d1ab402006-03-18 18:35:43 -0500382 struct deadline_data *dd = e->elevator_data; \
383 int __data = __VAR; \
Linus Torvalds1da177e2005-04-16 15:20:36 -0700384 if (__CONV) \
385 __data = jiffies_to_msecs(__data); \
386 return deadline_var_show(__data, (page)); \
387}
Al Viroe572ec72006-03-18 22:27:18 -0500388SHOW_FUNCTION(deadline_read_expire_show, dd->fifo_expire[READ], 1);
389SHOW_FUNCTION(deadline_write_expire_show, dd->fifo_expire[WRITE], 1);
390SHOW_FUNCTION(deadline_writes_starved_show, dd->writes_starved, 0);
391SHOW_FUNCTION(deadline_front_merges_show, dd->front_merges, 0);
392SHOW_FUNCTION(deadline_fifo_batch_show, dd->fifo_batch, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700393#undef SHOW_FUNCTION
394
395#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
Jens Axboeb374d182008-10-31 10:05:07 +0100396static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \
Linus Torvalds1da177e2005-04-16 15:20:36 -0700397{ \
Al Viro3d1ab402006-03-18 18:35:43 -0500398 struct deadline_data *dd = e->elevator_data; \
Linus Torvalds1da177e2005-04-16 15:20:36 -0700399 int __data; \
400 int ret = deadline_var_store(&__data, (page), count); \
401 if (__data < (MIN)) \
402 __data = (MIN); \
403 else if (__data > (MAX)) \
404 __data = (MAX); \
405 if (__CONV) \
406 *(__PTR) = msecs_to_jiffies(__data); \
407 else \
408 *(__PTR) = __data; \
409 return ret; \
410}
Al Viroe572ec72006-03-18 22:27:18 -0500411STORE_FUNCTION(deadline_read_expire_store, &dd->fifo_expire[READ], 0, INT_MAX, 1);
412STORE_FUNCTION(deadline_write_expire_store, &dd->fifo_expire[WRITE], 0, INT_MAX, 1);
413STORE_FUNCTION(deadline_writes_starved_store, &dd->writes_starved, INT_MIN, INT_MAX, 0);
414STORE_FUNCTION(deadline_front_merges_store, &dd->front_merges, 0, 1, 0);
415STORE_FUNCTION(deadline_fifo_batch_store, &dd->fifo_batch, 0, INT_MAX, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700416#undef STORE_FUNCTION
417
Al Viroe572ec72006-03-18 22:27:18 -0500418#define DD_ATTR(name) \
419 __ATTR(name, S_IRUGO|S_IWUSR, deadline_##name##_show, \
420 deadline_##name##_store)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700421
Al Viroe572ec72006-03-18 22:27:18 -0500422static struct elv_fs_entry deadline_attrs[] = {
423 DD_ATTR(read_expire),
424 DD_ATTR(write_expire),
425 DD_ATTR(writes_starved),
426 DD_ATTR(front_merges),
427 DD_ATTR(fifo_batch),
428 __ATTR_NULL
Linus Torvalds1da177e2005-04-16 15:20:36 -0700429};
430
Linus Torvalds1da177e2005-04-16 15:20:36 -0700431static struct elevator_type iosched_deadline = {
432 .ops = {
433 .elevator_merge_fn = deadline_merge,
434 .elevator_merged_fn = deadline_merged_request,
435 .elevator_merge_req_fn = deadline_merged_requests,
Jens Axboeb4878f22005-10-20 16:42:29 +0200436 .elevator_dispatch_fn = deadline_dispatch_requests,
437 .elevator_add_req_fn = deadline_add_request,
Jens Axboeb8aca352006-07-13 12:34:24 +0200438 .elevator_former_req_fn = elv_rb_former_request,
439 .elevator_latter_req_fn = elv_rb_latter_request,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700440 .elevator_init_fn = deadline_init_queue,
441 .elevator_exit_fn = deadline_exit_queue,
442 },
443
Al Viro3d1ab402006-03-18 18:35:43 -0500444 .elevator_attrs = deadline_attrs,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700445 .elevator_name = "deadline",
446 .elevator_owner = THIS_MODULE,
447};
448
449static int __init deadline_init(void)
450{
Adrian Bunk2fdd82b2007-12-12 18:51:56 +0100451 elv_register(&iosched_deadline);
452
453 return 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700454}
455
456static void __exit deadline_exit(void)
457{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700458 elv_unregister(&iosched_deadline);
459}
460
461module_init(deadline_init);
462module_exit(deadline_exit);
463
464MODULE_AUTHOR("Jens Axboe");
465MODULE_LICENSE("GPL");
466MODULE_DESCRIPTION("deadline IO scheduler");