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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 sector_t last_sector;
43 unsigned int starved;
44
45
46
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
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
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
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
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
133
134 if (dd->front_merges) {
135 sector_t sector = bio_end_sector(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
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
174
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
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 dd->last_sector = rq_end_sector(rq);
214
215
216
217
218
219 deadline_move_to_dispatch(dd, rq);
220}
221
222
223
224
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
232
233 if (time_after_eq(jiffies, rq_fifo_time(rq)))
234 return 1;
235
236 return 0;
237}
238
239
240
241
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
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
261 goto dispatch_request;
262
263
264
265
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
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
299
300 if (deadline_check_fifo(dd, data_dir) || !dd->next_rq[data_dir]) {
301
302
303
304
305
306 rq = rq_entry_fifo(dd->fifo_list[data_dir].next);
307 } else {
308
309
310
311
312 rq = dd->next_rq[data_dir];
313 }
314
315 dd->batching = 0;
316
317dispatch_request:
318
319
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
339
340static int deadline_init_queue(struct request_queue *q, struct elevator_type *e)
341{
342 struct deadline_data *dd;
343 struct elevator_queue *eq;
344
345 eq = elevator_alloc(q, e);
346 if (!eq)
347 return -ENOMEM;
348
349 dd = kmalloc_node(sizeof(*dd), GFP_KERNEL | __GFP_ZERO, q->node);
350 if (!dd) {
351 kobject_put(&eq->kobj);
352 return -ENOMEM;
353 }
354 eq->elevator_data = dd;
355
356 INIT_LIST_HEAD(&dd->fifo_list[READ]);
357 INIT_LIST_HEAD(&dd->fifo_list[WRITE]);
358 dd->sort_list[READ] = RB_ROOT;
359 dd->sort_list[WRITE] = RB_ROOT;
360 dd->fifo_expire[READ] = read_expire;
361 dd->fifo_expire[WRITE] = write_expire;
362 dd->writes_starved = writes_starved;
363 dd->front_merges = 1;
364 dd->fifo_batch = fifo_batch;
365
366 spin_lock_irq(q->queue_lock);
367 q->elevator = eq;
368 spin_unlock_irq(q->queue_lock);
369 return 0;
370}
371
372
373
374
375
376static ssize_t
377deadline_var_show(int var, char *page)
378{
379 return sprintf(page, "%d\n", var);
380}
381
382static ssize_t
383deadline_var_store(int *var, const char *page, size_t count)
384{
385 char *p = (char *) page;
386
387 *var = simple_strtol(p, &p, 10);
388 return count;
389}
390
391#define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
392static ssize_t __FUNC(struct elevator_queue *e, char *page) \
393{ \
394 struct deadline_data *dd = e->elevator_data; \
395 int __data = __VAR; \
396 if (__CONV) \
397 __data = jiffies_to_msecs(__data); \
398 return deadline_var_show(__data, (page)); \
399}
400SHOW_FUNCTION(deadline_read_expire_show, dd->fifo_expire[READ], 1);
401SHOW_FUNCTION(deadline_write_expire_show, dd->fifo_expire[WRITE], 1);
402SHOW_FUNCTION(deadline_writes_starved_show, dd->writes_starved, 0);
403SHOW_FUNCTION(deadline_front_merges_show, dd->front_merges, 0);
404SHOW_FUNCTION(deadline_fifo_batch_show, dd->fifo_batch, 0);
405#undef SHOW_FUNCTION
406
407#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
408static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \
409{ \
410 struct deadline_data *dd = e->elevator_data; \
411 int __data; \
412 int ret = deadline_var_store(&__data, (page), count); \
413 if (__data < (MIN)) \
414 __data = (MIN); \
415 else if (__data > (MAX)) \
416 __data = (MAX); \
417 if (__CONV) \
418 *(__PTR) = msecs_to_jiffies(__data); \
419 else \
420 *(__PTR) = __data; \
421 return ret; \
422}
423STORE_FUNCTION(deadline_read_expire_store, &dd->fifo_expire[READ], 0, INT_MAX, 1);
424STORE_FUNCTION(deadline_write_expire_store, &dd->fifo_expire[WRITE], 0, INT_MAX, 1);
425STORE_FUNCTION(deadline_writes_starved_store, &dd->writes_starved, INT_MIN, INT_MAX, 0);
426STORE_FUNCTION(deadline_front_merges_store, &dd->front_merges, 0, 1, 0);
427STORE_FUNCTION(deadline_fifo_batch_store, &dd->fifo_batch, 0, INT_MAX, 0);
428#undef STORE_FUNCTION
429
430#define DD_ATTR(name) \
431 __ATTR(name, S_IRUGO|S_IWUSR, deadline_##name##_show, \
432 deadline_##name##_store)
433
434static struct elv_fs_entry deadline_attrs[] = {
435 DD_ATTR(read_expire),
436 DD_ATTR(write_expire),
437 DD_ATTR(writes_starved),
438 DD_ATTR(front_merges),
439 DD_ATTR(fifo_batch),
440 __ATTR_NULL
441};
442
443static struct elevator_type iosched_deadline = {
444 .ops = {
445 .elevator_merge_fn = deadline_merge,
446 .elevator_merged_fn = deadline_merged_request,
447 .elevator_merge_req_fn = deadline_merged_requests,
448 .elevator_dispatch_fn = deadline_dispatch_requests,
449 .elevator_add_req_fn = deadline_add_request,
450 .elevator_former_req_fn = elv_rb_former_request,
451 .elevator_latter_req_fn = elv_rb_latter_request,
452 .elevator_init_fn = deadline_init_queue,
453 .elevator_exit_fn = deadline_exit_queue,
454 },
455
456 .elevator_attrs = deadline_attrs,
457 .elevator_name = "deadline",
458 .elevator_owner = THIS_MODULE,
459};
460
461static int __init deadline_init(void)
462{
463 return elv_register(&iosched_deadline);
464}
465
466static void __exit deadline_exit(void)
467{
468 elv_unregister(&iosched_deadline);
469}
470
471module_init(deadline_init);
472module_exit(deadline_exit);
473
474MODULE_AUTHOR("Jens Axboe");
475MODULE_LICENSE("GPL");
476MODULE_DESCRIPTION("deadline IO scheduler");
477