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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
19
20static const int read_expire = HZ / 2;
21static const int write_expire = 5 * HZ;
22static const int writes_starved = 2;
23static const int fifo_batch = 16;
24
25
26struct deadline_data {
27
28
29
30
31
32
33
34 struct rb_root sort_list[2];
35 struct list_head fifo_list[2];
36
37
38
39
40 struct request *next_rq[2];
41 unsigned int batching;
42 unsigned int starved;
43
44
45
46
47 int fifo_expire[2];
48 int fifo_batch;
49 int writes_starved;
50 int front_merges;
51};
52
53static void deadline_move_request(struct deadline_data *, struct request *);
54
55static inline struct rb_root *
56deadline_rb_root(struct deadline_data *dd, struct request *rq)
57{
58 return &dd->sort_list[rq_data_dir(rq)];
59}
60
61
62
63
64static inline struct request *
65deadline_latter_request(struct request *rq)
66{
67 struct rb_node *node = rb_next(&rq->rb_node);
68
69 if (node)
70 return rb_entry_rq(node);
71
72 return NULL;
73}
74
75static void
76deadline_add_rq_rb(struct deadline_data *dd, struct request *rq)
77{
78 struct rb_root *root = deadline_rb_root(dd, rq);
79
80 elv_rb_add(root, rq);
81}
82
83static inline void
84deadline_del_rq_rb(struct deadline_data *dd, struct request *rq)
85{
86 const int data_dir = rq_data_dir(rq);
87
88 if (dd->next_rq[data_dir] == rq)
89 dd->next_rq[data_dir] = deadline_latter_request(rq);
90
91 elv_rb_del(deadline_rb_root(dd, rq), rq);
92}
93
94
95
96
97static void
98deadline_add_request(struct request_queue *q, struct request *rq)
99{
100 struct deadline_data *dd = q->elevator->elevator_data;
101 const int data_dir = rq_data_dir(rq);
102
103 deadline_add_rq_rb(dd, rq);
104
105
106
107
108 rq->fifo_time = jiffies + dd->fifo_expire[data_dir];
109 list_add_tail(&rq->queuelist, &dd->fifo_list[data_dir]);
110}
111
112
113
114
115static void deadline_remove_request(struct request_queue *q, struct request *rq)
116{
117 struct deadline_data *dd = q->elevator->elevator_data;
118
119 rq_fifo_clear(rq);
120 deadline_del_rq_rb(dd, rq);
121}
122
123static int
124deadline_merge(struct request_queue *q, struct request **req, struct bio *bio)
125{
126 struct deadline_data *dd = q->elevator->elevator_data;
127 struct request *__rq;
128 int ret;
129
130
131
132
133 if (dd->front_merges) {
134 sector_t sector = bio_end_sector(bio);
135
136 __rq = elv_rb_find(&dd->sort_list[bio_data_dir(bio)], sector);
137 if (__rq) {
138 BUG_ON(sector != blk_rq_pos(__rq));
139
140 if (elv_bio_merge_ok(__rq, bio)) {
141 ret = ELEVATOR_FRONT_MERGE;
142 goto out;
143 }
144 }
145 }
146
147 return ELEVATOR_NO_MERGE;
148out:
149 *req = __rq;
150 return ret;
151}
152
153static void deadline_merged_request(struct request_queue *q,
154 struct request *req, int type)
155{
156 struct deadline_data *dd = q->elevator->elevator_data;
157
158
159
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
173
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
185
186 deadline_remove_request(q, next);
187}
188
189
190
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
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
214
215
216
217 deadline_move_to_dispatch(dd, rq);
218}
219
220
221
222
223
224static inline int deadline_check_fifo(struct deadline_data *dd, int ddir)
225{
226 struct request *rq = rq_entry_fifo(dd->fifo_list[ddir].next);
227
228
229
230
231 if (time_after_eq(jiffies, (unsigned long)rq->fifo_time))
232 return 1;
233
234 return 0;
235}
236
237
238
239
240
241static int deadline_dispatch_requests(struct request_queue *q, int force)
242{
243 struct deadline_data *dd = q->elevator->elevator_data;
244 const int reads = !list_empty(&dd->fifo_list[READ]);
245 const int writes = !list_empty(&dd->fifo_list[WRITE]);
246 struct request *rq;
247 int data_dir;
248
249
250
251
252 if (dd->next_rq[WRITE])
253 rq = dd->next_rq[WRITE];
254 else
255 rq = dd->next_rq[READ];
256
257 if (rq && dd->batching < dd->fifo_batch)
258
259 goto dispatch_request;
260
261
262
263
264
265
266 if (reads) {
267 BUG_ON(RB_EMPTY_ROOT(&dd->sort_list[READ]));
268
269 if (writes && (dd->starved++ >= dd->writes_starved))
270 goto dispatch_writes;
271
272 data_dir = READ;
273
274 goto dispatch_find_request;
275 }
276
277
278
279
280
281 if (writes) {
282dispatch_writes:
283 BUG_ON(RB_EMPTY_ROOT(&dd->sort_list[WRITE]));
284
285 dd->starved = 0;
286
287 data_dir = WRITE;
288
289 goto dispatch_find_request;
290 }
291
292 return 0;
293
294dispatch_find_request:
295
296
297
298 if (deadline_check_fifo(dd, data_dir) || !dd->next_rq[data_dir]) {
299
300
301
302
303
304 rq = rq_entry_fifo(dd->fifo_list[data_dir].next);
305 } else {
306
307
308
309
310 rq = dd->next_rq[data_dir];
311 }
312
313 dd->batching = 0;
314
315dispatch_request:
316
317
318
319 dd->batching++;
320 deadline_move_request(dd, rq);
321
322 return 1;
323}
324
325static void deadline_exit_queue(struct elevator_queue *e)
326{
327 struct deadline_data *dd = e->elevator_data;
328
329 BUG_ON(!list_empty(&dd->fifo_list[READ]));
330 BUG_ON(!list_empty(&dd->fifo_list[WRITE]));
331
332 kfree(dd);
333}
334
335
336
337
338static int deadline_init_queue(struct request_queue *q, struct elevator_type *e)
339{
340 struct deadline_data *dd;
341 struct elevator_queue *eq;
342
343 eq = elevator_alloc(q, e);
344 if (!eq)
345 return -ENOMEM;
346
347 dd = kzalloc_node(sizeof(*dd), GFP_KERNEL, q->node);
348 if (!dd) {
349 kobject_put(&eq->kobj);
350 return -ENOMEM;
351 }
352 eq->elevator_data = dd;
353
354 INIT_LIST_HEAD(&dd->fifo_list[READ]);
355 INIT_LIST_HEAD(&dd->fifo_list[WRITE]);
356 dd->sort_list[READ] = RB_ROOT;
357 dd->sort_list[WRITE] = RB_ROOT;
358 dd->fifo_expire[READ] = read_expire;
359 dd->fifo_expire[WRITE] = write_expire;
360 dd->writes_starved = writes_starved;
361 dd->front_merges = 1;
362 dd->fifo_batch = fifo_batch;
363
364 spin_lock_irq(q->queue_lock);
365 q->elevator = eq;
366 spin_unlock_irq(q->queue_lock);
367 return 0;
368}
369
370
371
372
373
374static ssize_t
375deadline_var_show(int var, char *page)
376{
377 return sprintf(page, "%d\n", var);
378}
379
380static ssize_t
381deadline_var_store(int *var, const char *page, size_t count)
382{
383 char *p = (char *) page;
384
385 *var = simple_strtol(p, &p, 10);
386 return count;
387}
388
389#define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
390static ssize_t __FUNC(struct elevator_queue *e, char *page) \
391{ \
392 struct deadline_data *dd = e->elevator_data; \
393 int __data = __VAR; \
394 if (__CONV) \
395 __data = jiffies_to_msecs(__data); \
396 return deadline_var_show(__data, (page)); \
397}
398SHOW_FUNCTION(deadline_read_expire_show, dd->fifo_expire[READ], 1);
399SHOW_FUNCTION(deadline_write_expire_show, dd->fifo_expire[WRITE], 1);
400SHOW_FUNCTION(deadline_writes_starved_show, dd->writes_starved, 0);
401SHOW_FUNCTION(deadline_front_merges_show, dd->front_merges, 0);
402SHOW_FUNCTION(deadline_fifo_batch_show, dd->fifo_batch, 0);
403#undef SHOW_FUNCTION
404
405#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
406static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \
407{ \
408 struct deadline_data *dd = e->elevator_data; \
409 int __data; \
410 int ret = deadline_var_store(&__data, (page), count); \
411 if (__data < (MIN)) \
412 __data = (MIN); \
413 else if (__data > (MAX)) \
414 __data = (MAX); \
415 if (__CONV) \
416 *(__PTR) = msecs_to_jiffies(__data); \
417 else \
418 *(__PTR) = __data; \
419 return ret; \
420}
421STORE_FUNCTION(deadline_read_expire_store, &dd->fifo_expire[READ], 0, INT_MAX, 1);
422STORE_FUNCTION(deadline_write_expire_store, &dd->fifo_expire[WRITE], 0, INT_MAX, 1);
423STORE_FUNCTION(deadline_writes_starved_store, &dd->writes_starved, INT_MIN, INT_MAX, 0);
424STORE_FUNCTION(deadline_front_merges_store, &dd->front_merges, 0, 1, 0);
425STORE_FUNCTION(deadline_fifo_batch_store, &dd->fifo_batch, 0, INT_MAX, 0);
426#undef STORE_FUNCTION
427
428#define DD_ATTR(name) \
429 __ATTR(name, S_IRUGO|S_IWUSR, deadline_##name##_show, \
430 deadline_##name##_store)
431
432static struct elv_fs_entry deadline_attrs[] = {
433 DD_ATTR(read_expire),
434 DD_ATTR(write_expire),
435 DD_ATTR(writes_starved),
436 DD_ATTR(front_merges),
437 DD_ATTR(fifo_batch),
438 __ATTR_NULL
439};
440
441static struct elevator_type iosched_deadline = {
442 .ops = {
443 .elevator_merge_fn = deadline_merge,
444 .elevator_merged_fn = deadline_merged_request,
445 .elevator_merge_req_fn = deadline_merged_requests,
446 .elevator_dispatch_fn = deadline_dispatch_requests,
447 .elevator_add_req_fn = deadline_add_request,
448 .elevator_former_req_fn = elv_rb_former_request,
449 .elevator_latter_req_fn = elv_rb_latter_request,
450 .elevator_init_fn = deadline_init_queue,
451 .elevator_exit_fn = deadline_exit_queue,
452 },
453
454 .elevator_attrs = deadline_attrs,
455 .elevator_name = "deadline",
456 .elevator_owner = THIS_MODULE,
457};
458
459static int __init deadline_init(void)
460{
461 return elv_register(&iosched_deadline);
462}
463
464static void __exit deadline_exit(void)
465{
466 elv_unregister(&iosched_deadline);
467}
468
469module_init(deadline_init);
470module_exit(deadline_exit);
471
472MODULE_AUTHOR("Jens Axboe");
473MODULE_LICENSE("GPL");
474MODULE_DESCRIPTION("deadline IO scheduler");
475