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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 struct request *__alias;
81
82 while (unlikely(__alias = elv_rb_add(root, rq)))
83 deadline_move_request(dd, __alias);
84}
85
86static inline void
87deadline_del_rq_rb(struct deadline_data *dd, struct request *rq)
88{
89 const int data_dir = rq_data_dir(rq);
90
91 if (dd->next_rq[data_dir] == rq)
92 dd->next_rq[data_dir] = deadline_latter_request(rq);
93
94 elv_rb_del(deadline_rb_root(dd, rq), rq);
95}
96
97
98
99
100static void
101deadline_add_request(struct request_queue *q, struct request *rq)
102{
103 struct deadline_data *dd = q->elevator->elevator_data;
104 const int data_dir = rq_data_dir(rq);
105
106 deadline_add_rq_rb(dd, rq);
107
108
109
110
111 rq_set_fifo_time(rq, jiffies + dd->fifo_expire[data_dir]);
112 list_add_tail(&rq->queuelist, &dd->fifo_list[data_dir]);
113}
114
115
116
117
118static void deadline_remove_request(struct request_queue *q, struct request *rq)
119{
120 struct deadline_data *dd = q->elevator->elevator_data;
121
122 rq_fifo_clear(rq);
123 deadline_del_rq_rb(dd, rq);
124}
125
126static int
127deadline_merge(struct request_queue *q, struct request **req, struct bio *bio)
128{
129 struct deadline_data *dd = q->elevator->elevator_data;
130 struct request *__rq;
131 int ret;
132
133
134
135
136 if (dd->front_merges) {
137 sector_t sector = bio->bi_sector + bio_sectors(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_rq_merge_ok(__rq, bio)) {
144 ret = ELEVATOR_FRONT_MERGE;
145 goto out;
146 }
147 }
148 }
149
150 return ELEVATOR_NO_MERGE;
151out:
152 *req = __rq;
153 return ret;
154}
155
156static void deadline_merged_request(struct request_queue *q,
157 struct request *req, int type)
158{
159 struct deadline_data *dd = q->elevator->elevator_data;
160
161
162
163
164 if (type == ELEVATOR_FRONT_MERGE) {
165 elv_rb_del(deadline_rb_root(dd, req), req);
166 deadline_add_rq_rb(dd, req);
167 }
168}
169
170static void
171deadline_merged_requests(struct request_queue *q, struct request *req,
172 struct request *next)
173{
174
175
176
177
178 if (!list_empty(&req->queuelist) && !list_empty(&next->queuelist)) {
179 if (time_before(rq_fifo_time(next), rq_fifo_time(req))) {
180 list_move(&req->queuelist, &next->queuelist);
181 rq_set_fifo_time(req, rq_fifo_time(next));
182 }
183 }
184
185
186
187
188 deadline_remove_request(q, next);
189}
190
191
192
193
194static inline void
195deadline_move_to_dispatch(struct deadline_data *dd, struct request *rq)
196{
197 struct request_queue *q = rq->q;
198
199 deadline_remove_request(q, rq);
200 elv_dispatch_add_tail(q, rq);
201}
202
203
204
205
206static void
207deadline_move_request(struct deadline_data *dd, struct request *rq)
208{
209 const int data_dir = rq_data_dir(rq);
210
211 dd->next_rq[READ] = NULL;
212 dd->next_rq[WRITE] = NULL;
213 dd->next_rq[data_dir] = deadline_latter_request(rq);
214
215 dd->last_sector = rq_end_sector(rq);
216
217
218
219
220
221 deadline_move_to_dispatch(dd, rq);
222}
223
224
225
226
227
228static inline int deadline_check_fifo(struct deadline_data *dd, int ddir)
229{
230 struct request *rq = rq_entry_fifo(dd->fifo_list[ddir].next);
231
232
233
234
235 if (time_after(jiffies, rq_fifo_time(rq)))
236 return 1;
237
238 return 0;
239}
240
241
242
243
244
245static int deadline_dispatch_requests(struct request_queue *q, int force)
246{
247 struct deadline_data *dd = q->elevator->elevator_data;
248 const int reads = !list_empty(&dd->fifo_list[READ]);
249 const int writes = !list_empty(&dd->fifo_list[WRITE]);
250 struct request *rq;
251 int data_dir;
252
253
254
255
256 if (dd->next_rq[WRITE])
257 rq = dd->next_rq[WRITE];
258 else
259 rq = dd->next_rq[READ];
260
261 if (rq && dd->batching < dd->fifo_batch)
262
263 goto dispatch_request;
264
265
266
267
268
269
270 if (reads) {
271 BUG_ON(RB_EMPTY_ROOT(&dd->sort_list[READ]));
272
273 if (writes && (dd->starved++ >= dd->writes_starved))
274 goto dispatch_writes;
275
276 data_dir = READ;
277
278 goto dispatch_find_request;
279 }
280
281
282
283
284
285 if (writes) {
286dispatch_writes:
287 BUG_ON(RB_EMPTY_ROOT(&dd->sort_list[WRITE]));
288
289 dd->starved = 0;
290
291 data_dir = WRITE;
292
293 goto dispatch_find_request;
294 }
295
296 return 0;
297
298dispatch_find_request:
299
300
301
302 if (deadline_check_fifo(dd, data_dir) || !dd->next_rq[data_dir]) {
303
304
305
306
307
308 rq = rq_entry_fifo(dd->fifo_list[data_dir].next);
309 } else {
310
311
312
313
314 rq = dd->next_rq[data_dir];
315 }
316
317 dd->batching = 0;
318
319dispatch_request:
320
321
322
323 dd->batching++;
324 deadline_move_request(dd, rq);
325
326 return 1;
327}
328
329static void deadline_exit_queue(struct elevator_queue *e)
330{
331 struct deadline_data *dd = e->elevator_data;
332
333 BUG_ON(!list_empty(&dd->fifo_list[READ]));
334 BUG_ON(!list_empty(&dd->fifo_list[WRITE]));
335
336 kfree(dd);
337}
338
339
340
341
342static void *deadline_init_queue(struct request_queue *q)
343{
344 struct deadline_data *dd;
345
346 dd = kmalloc_node(sizeof(*dd), GFP_KERNEL | __GFP_ZERO, q->node);
347 if (!dd)
348 return NULL;
349
350 INIT_LIST_HEAD(&dd->fifo_list[READ]);
351 INIT_LIST_HEAD(&dd->fifo_list[WRITE]);
352 dd->sort_list[READ] = RB_ROOT;
353 dd->sort_list[WRITE] = RB_ROOT;
354 dd->fifo_expire[READ] = read_expire;
355 dd->fifo_expire[WRITE] = write_expire;
356 dd->writes_starved = writes_starved;
357 dd->front_merges = 1;
358 dd->fifo_batch = fifo_batch;
359 return dd;
360}
361
362
363
364
365
366static ssize_t
367deadline_var_show(int var, char *page)
368{
369 return sprintf(page, "%d\n", var);
370}
371
372static ssize_t
373deadline_var_store(int *var, const char *page, size_t count)
374{
375 char *p = (char *) page;
376
377 *var = simple_strtol(p, &p, 10);
378 return count;
379}
380
381#define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
382static ssize_t __FUNC(struct elevator_queue *e, char *page) \
383{ \
384 struct deadline_data *dd = e->elevator_data; \
385 int __data = __VAR; \
386 if (__CONV) \
387 __data = jiffies_to_msecs(__data); \
388 return deadline_var_show(__data, (page)); \
389}
390SHOW_FUNCTION(deadline_read_expire_show, dd->fifo_expire[READ], 1);
391SHOW_FUNCTION(deadline_write_expire_show, dd->fifo_expire[WRITE], 1);
392SHOW_FUNCTION(deadline_writes_starved_show, dd->writes_starved, 0);
393SHOW_FUNCTION(deadline_front_merges_show, dd->front_merges, 0);
394SHOW_FUNCTION(deadline_fifo_batch_show, dd->fifo_batch, 0);
395#undef SHOW_FUNCTION
396
397#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
398static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \
399{ \
400 struct deadline_data *dd = e->elevator_data; \
401 int __data; \
402 int ret = deadline_var_store(&__data, (page), count); \
403 if (__data < (MIN)) \
404 __data = (MIN); \
405 else if (__data > (MAX)) \
406 __data = (MAX); \
407 if (__CONV) \
408 *(__PTR) = msecs_to_jiffies(__data); \
409 else \
410 *(__PTR) = __data; \
411 return ret; \
412}
413STORE_FUNCTION(deadline_read_expire_store, &dd->fifo_expire[READ], 0, INT_MAX, 1);
414STORE_FUNCTION(deadline_write_expire_store, &dd->fifo_expire[WRITE], 0, INT_MAX, 1);
415STORE_FUNCTION(deadline_writes_starved_store, &dd->writes_starved, INT_MIN, INT_MAX, 0);
416STORE_FUNCTION(deadline_front_merges_store, &dd->front_merges, 0, 1, 0);
417STORE_FUNCTION(deadline_fifo_batch_store, &dd->fifo_batch, 0, INT_MAX, 0);
418#undef STORE_FUNCTION
419
420#define DD_ATTR(name) \
421 __ATTR(name, S_IRUGO|S_IWUSR, deadline_##name##_show, \
422 deadline_##name##_store)
423
424static struct elv_fs_entry deadline_attrs[] = {
425 DD_ATTR(read_expire),
426 DD_ATTR(write_expire),
427 DD_ATTR(writes_starved),
428 DD_ATTR(front_merges),
429 DD_ATTR(fifo_batch),
430 __ATTR_NULL
431};
432
433static struct elevator_type iosched_deadline = {
434 .ops = {
435 .elevator_merge_fn = deadline_merge,
436 .elevator_merged_fn = deadline_merged_request,
437 .elevator_merge_req_fn = deadline_merged_requests,
438 .elevator_dispatch_fn = deadline_dispatch_requests,
439 .elevator_add_req_fn = deadline_add_request,
440 .elevator_former_req_fn = elv_rb_former_request,
441 .elevator_latter_req_fn = elv_rb_latter_request,
442 .elevator_init_fn = deadline_init_queue,
443 .elevator_exit_fn = deadline_exit_queue,
444 },
445
446 .elevator_attrs = deadline_attrs,
447 .elevator_name = "deadline",
448 .elevator_owner = THIS_MODULE,
449};
450
451static int __init deadline_init(void)
452{
453 elv_register(&iosched_deadline);
454
455 return 0;
456}
457
458static void __exit deadline_exit(void)
459{
460 elv_unregister(&iosched_deadline);
461}
462
463module_init(deadline_init);
464module_exit(deadline_exit);
465
466MODULE_AUTHOR("Jens Axboe");
467MODULE_LICENSE("GPL");
468MODULE_DESCRIPTION("deadline IO scheduler");
469