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1/*
2 * Deadline i/o scheduler.
3 *
4 * Copyright (C) 2002 Jens Axboe <axboe@kernel.dk>
5 */
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>
11#include <linux/module.h>
12#include <linux/slab.h>
13#include <linux/init.h>
14#include <linux/compiler.h>
15#include <linux/rbtree.h>
16
17/*
18 * See Documentation/block/deadline-iosched.txt
19 */
20static 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
24 by the above parameters. For throughput. */
25
26struct 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];
36
37 /*
38 * next in sort order. read, write or both are NULL
39 */
40 struct request *next_rq[2];
41 unsigned int batching; /* number of sequential requests made */
42 unsigned int starved; /* times reads have starved writes */
43
44 /*
45 * settings that change how the i/o scheduler behaves
46 */
47 int fifo_expire[2];
48 int fifo_batch;
49 int writes_starved;
50 int front_merges;
51};
52
53static inline struct rb_root *
54deadline_rb_root(struct deadline_data *dd, struct request *rq)
55{
56 return &dd->sort_list[rq_data_dir(rq)];
57}
58
59/*
60 * get the request after `rq' in sector-sorted order
61 */
62static inline struct request *
63deadline_latter_request(struct request *rq)
64{
65 struct rb_node *node = rb_next(&rq->rb_node);
66
67 if (node)
68 return rb_entry_rq(node);
69
70 return NULL;
71}
72
73static void
74deadline_add_rq_rb(struct deadline_data *dd, struct request *rq)
75{
76 struct rb_root *root = deadline_rb_root(dd, rq);
77
78 elv_rb_add(root, rq);
79}
80
81static inline void
82deadline_del_rq_rb(struct deadline_data *dd, struct request *rq)
83{
84 const int data_dir = rq_data_dir(rq);
85
86 if (dd->next_rq[data_dir] == rq)
87 dd->next_rq[data_dir] = deadline_latter_request(rq);
88
89 elv_rb_del(deadline_rb_root(dd, rq), rq);
90}
91
92/*
93 * add rq to rbtree and fifo
94 */
95static void
96deadline_add_request(struct request_queue *q, struct request *rq)
97{
98 struct deadline_data *dd = q->elevator->elevator_data;
99 const int data_dir = rq_data_dir(rq);
100
101 /*
102 * This may be a requeue of a write request that has locked its
103 * target zone. If it is the case, this releases the zone lock.
104 */
105 blk_req_zone_write_unlock(rq);
106
107 deadline_add_rq_rb(dd, rq);
108
109 /*
110 * set expire time and add to fifo list
111 */
112 rq->fifo_time = jiffies + dd->fifo_expire[data_dir];
113 list_add_tail(&rq->queuelist, &dd->fifo_list[data_dir]);
114}
115
116/*
117 * remove rq from rbtree and fifo.
118 */
119static void deadline_remove_request(struct request_queue *q, struct request *rq)
120{
121 struct deadline_data *dd = q->elevator->elevator_data;
122
123 rq_fifo_clear(rq);
124 deadline_del_rq_rb(dd, rq);
125}
126
127static enum elv_merge
128deadline_merge(struct request_queue *q, struct request **req, struct bio *bio)
129{
130 struct deadline_data *dd = q->elevator->elevator_data;
131 struct request *__rq;
132
133 /*
134 * check for front merge
135 */
136 if (dd->front_merges) {
137 sector_t sector = bio_end_sector(bio);
138
139 __rq = elv_rb_find(&dd->sort_list[bio_data_dir(bio)], sector);
140 if (__rq) {
141 BUG_ON(sector != blk_rq_pos(__rq));
142
143 if (elv_bio_merge_ok(__rq, bio)) {
144 *req = __rq;
145 return ELEVATOR_FRONT_MERGE;
146 }
147 }
148 }
149
150 return ELEVATOR_NO_MERGE;
151}
152
153static void deadline_merged_request(struct request_queue *q,
154 struct request *req, enum elv_merge type)
155{
156 struct deadline_data *dd = q->elevator->elevator_data;
157
158 /*
159 * if the merge was a front merge, we need to reposition request
160 */
161 if (type == ELEVATOR_FRONT_MERGE) {
162 elv_rb_del(deadline_rb_root(dd, req), req);
163 deadline_add_rq_rb(dd, req);
164 }
165}
166
167static void
168deadline_merged_requests(struct request_queue *q, struct request *req,
169 struct request *next)
170{
171 /*
172 * if next expires before rq, assign its expire time to rq
173 * and move into next position (next will be deleted) in fifo
174 */
175 if (!list_empty(&req->queuelist) && !list_empty(&next->queuelist)) {
176 if (time_before((unsigned long)next->fifo_time,
177 (unsigned long)req->fifo_time)) {
178 list_move(&req->queuelist, &next->queuelist);
179 req->fifo_time = next->fifo_time;
180 }
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
193deadline_move_to_dispatch(struct deadline_data *dd, struct request *rq)
194{
195 struct request_queue *q = rq->q;
196
197 /*
198 * For a zoned block device, write requests must write lock their
199 * target zone.
200 */
201 blk_req_zone_write_lock(rq);
202
203 deadline_remove_request(q, rq);
204 elv_dispatch_add_tail(q, rq);
205}
206
207/*
208 * move an entry to dispatch queue
209 */
210static void
211deadline_move_request(struct deadline_data *dd, struct request *rq)
212{
213 const int data_dir = rq_data_dir(rq);
214
215 dd->next_rq[READ] = NULL;
216 dd->next_rq[WRITE] = NULL;
217 dd->next_rq[data_dir] = deadline_latter_request(rq);
218
219 /*
220 * take it off the sort and fifo list, move
221 * to dispatch queue
222 */
223 deadline_move_to_dispatch(dd, rq);
224}
225
226/*
227 * deadline_check_fifo returns 0 if there are no expired requests on the fifo,
228 * 1 otherwise. Requires !list_empty(&dd->fifo_list[data_dir])
229 */
230static inline int deadline_check_fifo(struct deadline_data *dd, int ddir)
231{
232 struct request *rq = rq_entry_fifo(dd->fifo_list[ddir].next);
233
234 /*
235 * rq is expired!
236 */
237 if (time_after_eq(jiffies, (unsigned long)rq->fifo_time))
238 return 1;
239
240 return 0;
241}
242
243/*
244 * For the specified data direction, return the next request to dispatch using
245 * arrival ordered lists.
246 */
247static struct request *
248deadline_fifo_request(struct deadline_data *dd, int data_dir)
249{
250 struct request *rq;
251
252 if (WARN_ON_ONCE(data_dir != READ && data_dir != WRITE))
253 return NULL;
254
255 if (list_empty(&dd->fifo_list[data_dir]))
256 return NULL;
257
258 rq = rq_entry_fifo(dd->fifo_list[data_dir].next);
259 if (data_dir == READ || !blk_queue_is_zoned(rq->q))
260 return rq;
261
262 /*
263 * Look for a write request that can be dispatched, that is one with
264 * an unlocked target zone.
265 */
266 list_for_each_entry(rq, &dd->fifo_list[WRITE], queuelist) {
267 if (blk_req_can_dispatch_to_zone(rq))
268 return rq;
269 }
270
271 return NULL;
272}
273
274/*
275 * For the specified data direction, return the next request to dispatch using
276 * sector position sorted lists.
277 */
278static struct request *
279deadline_next_request(struct deadline_data *dd, int data_dir)
280{
281 struct request *rq;
282
283 if (WARN_ON_ONCE(data_dir != READ && data_dir != WRITE))
284 return NULL;
285
286 rq = dd->next_rq[data_dir];
287 if (!rq)
288 return NULL;
289
290 if (data_dir == READ || !blk_queue_is_zoned(rq->q))
291 return rq;
292
293 /*
294 * Look for a write request that can be dispatched, that is one with
295 * an unlocked target zone.
296 */
297 while (rq) {
298 if (blk_req_can_dispatch_to_zone(rq))
299 return rq;
300 rq = deadline_latter_request(rq);
301 }
302
303 return NULL;
304}
305
306/*
307 * deadline_dispatch_requests selects the best request according to
308 * read/write expire, fifo_batch, etc
309 */
310static int deadline_dispatch_requests(struct request_queue *q, int force)
311{
312 struct deadline_data *dd = q->elevator->elevator_data;
313 const int reads = !list_empty(&dd->fifo_list[READ]);
314 const int writes = !list_empty(&dd->fifo_list[WRITE]);
315 struct request *rq, *next_rq;
316 int data_dir;
317
318 /*
319 * batches are currently reads XOR writes
320 */
321 rq = deadline_next_request(dd, WRITE);
322 if (!rq)
323 rq = deadline_next_request(dd, READ);
324
325 if (rq && dd->batching < dd->fifo_batch)
326 /* we have a next request are still entitled to batch */
327 goto dispatch_request;
328
329 /*
330 * at this point we are not running a batch. select the appropriate
331 * data direction (read / write)
332 */
333
334 if (reads) {
335 BUG_ON(RB_EMPTY_ROOT(&dd->sort_list[READ]));
336
337 if (deadline_fifo_request(dd, WRITE) &&
338 (dd->starved++ >= dd->writes_starved))
339 goto dispatch_writes;
340
341 data_dir = READ;
342
343 goto dispatch_find_request;
344 }
345
346 /*
347 * there are either no reads or writes have been starved
348 */
349
350 if (writes) {
351dispatch_writes:
352 BUG_ON(RB_EMPTY_ROOT(&dd->sort_list[WRITE]));
353
354 dd->starved = 0;
355
356 data_dir = WRITE;
357
358 goto dispatch_find_request;
359 }
360
361 return 0;
362
363dispatch_find_request:
364 /*
365 * we are not running a batch, find best request for selected data_dir
366 */
367 next_rq = deadline_next_request(dd, data_dir);
368 if (deadline_check_fifo(dd, data_dir) || !next_rq) {
369 /*
370 * A deadline has expired, the last request was in the other
371 * direction, or we have run out of higher-sectored requests.
372 * Start again from the request with the earliest expiry time.
373 */
374 rq = deadline_fifo_request(dd, data_dir);
375 } else {
376 /*
377 * The last req was the same dir and we have a next request in
378 * sort order. No expired requests so continue on from here.
379 */
380 rq = next_rq;
381 }
382
383 /*
384 * For a zoned block device, if we only have writes queued and none of
385 * them can be dispatched, rq will be NULL.
386 */
387 if (!rq)
388 return 0;
389
390 dd->batching = 0;
391
392dispatch_request:
393 /*
394 * rq is the selected appropriate request.
395 */
396 dd->batching++;
397 deadline_move_request(dd, rq);
398
399 return 1;
400}
401
402/*
403 * For zoned block devices, write unlock the target zone of completed
404 * write requests.
405 */
406static void
407deadline_completed_request(struct request_queue *q, struct request *rq)
408{
409 blk_req_zone_write_unlock(rq);
410}
411
412static void deadline_exit_queue(struct elevator_queue *e)
413{
414 struct deadline_data *dd = e->elevator_data;
415
416 BUG_ON(!list_empty(&dd->fifo_list[READ]));
417 BUG_ON(!list_empty(&dd->fifo_list[WRITE]));
418
419 kfree(dd);
420}
421
422/*
423 * initialize elevator private data (deadline_data).
424 */
425static int deadline_init_queue(struct request_queue *q, struct elevator_type *e)
426{
427 struct deadline_data *dd;
428 struct elevator_queue *eq;
429
430 eq = elevator_alloc(q, e);
431 if (!eq)
432 return -ENOMEM;
433
434 dd = kzalloc_node(sizeof(*dd), GFP_KERNEL, q->node);
435 if (!dd) {
436 kobject_put(&eq->kobj);
437 return -ENOMEM;
438 }
439 eq->elevator_data = dd;
440
441 INIT_LIST_HEAD(&dd->fifo_list[READ]);
442 INIT_LIST_HEAD(&dd->fifo_list[WRITE]);
443 dd->sort_list[READ] = RB_ROOT;
444 dd->sort_list[WRITE] = RB_ROOT;
445 dd->fifo_expire[READ] = read_expire;
446 dd->fifo_expire[WRITE] = write_expire;
447 dd->writes_starved = writes_starved;
448 dd->front_merges = 1;
449 dd->fifo_batch = fifo_batch;
450
451 spin_lock_irq(q->queue_lock);
452 q->elevator = eq;
453 spin_unlock_irq(q->queue_lock);
454 return 0;
455}
456
457/*
458 * sysfs parts below
459 */
460
461static ssize_t
462deadline_var_show(int var, char *page)
463{
464 return sprintf(page, "%d\n", var);
465}
466
467static void
468deadline_var_store(int *var, const char *page)
469{
470 char *p = (char *) page;
471
472 *var = simple_strtol(p, &p, 10);
473}
474
475#define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
476static ssize_t __FUNC(struct elevator_queue *e, char *page) \
477{ \
478 struct deadline_data *dd = e->elevator_data; \
479 int __data = __VAR; \
480 if (__CONV) \
481 __data = jiffies_to_msecs(__data); \
482 return deadline_var_show(__data, (page)); \
483}
484SHOW_FUNCTION(deadline_read_expire_show, dd->fifo_expire[READ], 1);
485SHOW_FUNCTION(deadline_write_expire_show, dd->fifo_expire[WRITE], 1);
486SHOW_FUNCTION(deadline_writes_starved_show, dd->writes_starved, 0);
487SHOW_FUNCTION(deadline_front_merges_show, dd->front_merges, 0);
488SHOW_FUNCTION(deadline_fifo_batch_show, dd->fifo_batch, 0);
489#undef SHOW_FUNCTION
490
491#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
492static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \
493{ \
494 struct deadline_data *dd = e->elevator_data; \
495 int __data; \
496 deadline_var_store(&__data, (page)); \
497 if (__data < (MIN)) \
498 __data = (MIN); \
499 else if (__data > (MAX)) \
500 __data = (MAX); \
501 if (__CONV) \
502 *(__PTR) = msecs_to_jiffies(__data); \
503 else \
504 *(__PTR) = __data; \
505 return count; \
506}
507STORE_FUNCTION(deadline_read_expire_store, &dd->fifo_expire[READ], 0, INT_MAX, 1);
508STORE_FUNCTION(deadline_write_expire_store, &dd->fifo_expire[WRITE], 0, INT_MAX, 1);
509STORE_FUNCTION(deadline_writes_starved_store, &dd->writes_starved, INT_MIN, INT_MAX, 0);
510STORE_FUNCTION(deadline_front_merges_store, &dd->front_merges, 0, 1, 0);
511STORE_FUNCTION(deadline_fifo_batch_store, &dd->fifo_batch, 0, INT_MAX, 0);
512#undef STORE_FUNCTION
513
514#define DD_ATTR(name) \
515 __ATTR(name, S_IRUGO|S_IWUSR, deadline_##name##_show, \
516 deadline_##name##_store)
517
518static struct elv_fs_entry deadline_attrs[] = {
519 DD_ATTR(read_expire),
520 DD_ATTR(write_expire),
521 DD_ATTR(writes_starved),
522 DD_ATTR(front_merges),
523 DD_ATTR(fifo_batch),
524 __ATTR_NULL
525};
526
527static struct elevator_type iosched_deadline = {
528 .ops.sq = {
529 .elevator_merge_fn = deadline_merge,
530 .elevator_merged_fn = deadline_merged_request,
531 .elevator_merge_req_fn = deadline_merged_requests,
532 .elevator_dispatch_fn = deadline_dispatch_requests,
533 .elevator_completed_req_fn = deadline_completed_request,
534 .elevator_add_req_fn = deadline_add_request,
535 .elevator_former_req_fn = elv_rb_former_request,
536 .elevator_latter_req_fn = elv_rb_latter_request,
537 .elevator_init_fn = deadline_init_queue,
538 .elevator_exit_fn = deadline_exit_queue,
539 },
540
541 .elevator_attrs = deadline_attrs,
542 .elevator_name = "deadline",
543 .elevator_owner = THIS_MODULE,
544};
545
546static int __init deadline_init(void)
547{
548 return elv_register(&iosched_deadline);
549}
550
551static void __exit deadline_exit(void)
552{
553 elv_unregister(&iosched_deadline);
554}
555
556module_init(deadline_init);
557module_exit(deadline_exit);
558
559MODULE_AUTHOR("Jens Axboe");
560MODULE_LICENSE("GPL");
561MODULE_DESCRIPTION("deadline IO scheduler");
1/*
2 * Deadline i/o scheduler.
3 *
4 * Copyright (C) 2002 Jens Axboe <axboe@kernel.dk>
5 */
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>
11#include <linux/module.h>
12#include <linux/slab.h>
13#include <linux/init.h>
14#include <linux/compiler.h>
15#include <linux/rbtree.h>
16
17/*
18 * See Documentation/block/deadline-iosched.txt
19 */
20static 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
24 by the above parameters. For throughput. */
25
26struct 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];
36
37 /*
38 * next in sort order. read, write or both are NULL
39 */
40 struct request *next_rq[2];
41 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;
52};
53
54static void deadline_move_request(struct deadline_data *, struct request *);
55
56static 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}
61
62/*
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
76static void
77deadline_add_rq_rb(struct deadline_data *dd, struct request *rq)
78{
79 struct rb_root *root = deadline_rb_root(dd, rq);
80
81 elv_rb_add(root, rq);
82}
83
84static inline void
85deadline_del_rq_rb(struct deadline_data *dd, struct request *rq)
86{
87 const int data_dir = rq_data_dir(rq);
88
89 if (dd->next_rq[data_dir] == rq)
90 dd->next_rq[data_dir] = deadline_latter_request(rq);
91
92 elv_rb_del(deadline_rb_root(dd, rq), rq);
93}
94
95/*
96 * add rq to rbtree and fifo
97 */
98static void
99deadline_add_request(struct request_queue *q, struct request *rq)
100{
101 struct deadline_data *dd = q->elevator->elevator_data;
102 const int data_dir = rq_data_dir(rq);
103
104 deadline_add_rq_rb(dd, rq);
105
106 /*
107 * set expire time and add to fifo list
108 */
109 rq_set_fifo_time(rq, jiffies + dd->fifo_expire[data_dir]);
110 list_add_tail(&rq->queuelist, &dd->fifo_list[data_dir]);
111}
112
113/*
114 * remove rq from rbtree and fifo.
115 */
116static void deadline_remove_request(struct request_queue *q, struct request *rq)
117{
118 struct deadline_data *dd = q->elevator->elevator_data;
119
120 rq_fifo_clear(rq);
121 deadline_del_rq_rb(dd, rq);
122}
123
124static int
125deadline_merge(struct request_queue *q, struct request **req, struct bio *bio)
126{
127 struct deadline_data *dd = q->elevator->elevator_data;
128 struct request *__rq;
129 int ret;
130
131 /*
132 * check for front merge
133 */
134 if (dd->front_merges) {
135 sector_t sector = bio->bi_sector + bio_sectors(bio);
136
137 __rq = elv_rb_find(&dd->sort_list[bio_data_dir(bio)], sector);
138 if (__rq) {
139 BUG_ON(sector != blk_rq_pos(__rq));
140
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:
150 *req = __rq;
151 return ret;
152}
153
154static void deadline_merged_request(struct request_queue *q,
155 struct request *req, int type)
156{
157 struct deadline_data *dd = q->elevator->elevator_data;
158
159 /*
160 * if the merge was a front merge, we need to reposition request
161 */
162 if (type == ELEVATOR_FRONT_MERGE) {
163 elv_rb_del(deadline_rb_root(dd, req), req);
164 deadline_add_rq_rb(dd, req);
165 }
166}
167
168static void
169deadline_merged_requests(struct request_queue *q, struct request *req,
170 struct request *next)
171{
172 /*
173 * if next expires before rq, assign its expire time to rq
174 * and move into next position (next will be deleted) in fifo
175 */
176 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));
180 }
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
193deadline_move_to_dispatch(struct deadline_data *dd, struct request *rq)
194{
195 struct request_queue *q = rq->q;
196
197 deadline_remove_request(q, rq);
198 elv_dispatch_add_tail(q, rq);
199}
200
201/*
202 * move an entry to dispatch queue
203 */
204static void
205deadline_move_request(struct deadline_data *dd, struct request *rq)
206{
207 const int data_dir = rq_data_dir(rq);
208
209 dd->next_rq[READ] = NULL;
210 dd->next_rq[WRITE] = NULL;
211 dd->next_rq[data_dir] = deadline_latter_request(rq);
212
213 dd->last_sector = rq_end_sector(rq);
214
215 /*
216 * take it off the sort and fifo list, move
217 * to dispatch queue
218 */
219 deadline_move_to_dispatch(dd, rq);
220}
221
222/*
223 * deadline_check_fifo returns 0 if there are no expired requests on the fifo,
224 * 1 otherwise. Requires !list_empty(&dd->fifo_list[data_dir])
225 */
226static inline int deadline_check_fifo(struct deadline_data *dd, int ddir)
227{
228 struct request *rq = rq_entry_fifo(dd->fifo_list[ddir].next);
229
230 /*
231 * rq is expired!
232 */
233 if (time_after(jiffies, rq_fifo_time(rq)))
234 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 */
243static int deadline_dispatch_requests(struct request_queue *q, int force)
244{
245 struct deadline_data *dd = q->elevator->elevator_data;
246 const int reads = !list_empty(&dd->fifo_list[READ]);
247 const int writes = !list_empty(&dd->fifo_list[WRITE]);
248 struct request *rq;
249 int data_dir;
250
251 /*
252 * batches are currently reads XOR writes
253 */
254 if (dd->next_rq[WRITE])
255 rq = dd->next_rq[WRITE];
256 else
257 rq = dd->next_rq[READ];
258
259 if (rq && dd->batching < dd->fifo_batch)
260 /* we have a next request are still entitled to batch */
261 goto dispatch_request;
262
263 /*
264 * at this point we are not running a batch. select the appropriate
265 * data direction (read / write)
266 */
267
268 if (reads) {
269 BUG_ON(RB_EMPTY_ROOT(&dd->sort_list[READ]));
270
271 if (writes && (dd->starved++ >= dd->writes_starved))
272 goto dispatch_writes;
273
274 data_dir = READ;
275
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:
285 BUG_ON(RB_EMPTY_ROOT(&dd->sort_list[WRITE]));
286
287 dd->starved = 0;
288
289 data_dir = WRITE;
290
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 */
300 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 */
306 rq = rq_entry_fifo(dd->fifo_list[data_dir].next);
307 } else {
308 /*
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 */
312 rq = dd->next_rq[data_dir];
313 }
314
315 dd->batching = 0;
316
317dispatch_request:
318 /*
319 * rq is the selected appropriate request.
320 */
321 dd->batching++;
322 deadline_move_request(dd, rq);
323
324 return 1;
325}
326
327static void deadline_exit_queue(struct elevator_queue *e)
328{
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
334 kfree(dd);
335}
336
337/*
338 * initialize elevator private data (deadline_data).
339 */
340static void *deadline_init_queue(struct request_queue *q)
341{
342 struct deadline_data *dd;
343
344 dd = kmalloc_node(sizeof(*dd), GFP_KERNEL | __GFP_ZERO, q->node);
345 if (!dd)
346 return NULL;
347
348 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;
352 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;
357 return dd;
358}
359
360/*
361 * sysfs parts below
362 */
363
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) \
380static ssize_t __FUNC(struct elevator_queue *e, char *page) \
381{ \
382 struct deadline_data *dd = e->elevator_data; \
383 int __data = __VAR; \
384 if (__CONV) \
385 __data = jiffies_to_msecs(__data); \
386 return deadline_var_show(__data, (page)); \
387}
388SHOW_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);
393#undef SHOW_FUNCTION
394
395#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
396static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \
397{ \
398 struct deadline_data *dd = e->elevator_data; \
399 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}
411STORE_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);
416#undef STORE_FUNCTION
417
418#define DD_ATTR(name) \
419 __ATTR(name, S_IRUGO|S_IWUSR, deadline_##name##_show, \
420 deadline_##name##_store)
421
422static 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
429};
430
431static 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,
436 .elevator_dispatch_fn = deadline_dispatch_requests,
437 .elevator_add_req_fn = deadline_add_request,
438 .elevator_former_req_fn = elv_rb_former_request,
439 .elevator_latter_req_fn = elv_rb_latter_request,
440 .elevator_init_fn = deadline_init_queue,
441 .elevator_exit_fn = deadline_exit_queue,
442 },
443
444 .elevator_attrs = deadline_attrs,
445 .elevator_name = "deadline",
446 .elevator_owner = THIS_MODULE,
447};
448
449static int __init deadline_init(void)
450{
451 elv_register(&iosched_deadline);
452
453 return 0;
454}
455
456static void __exit deadline_exit(void)
457{
458 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");