Commit | Line | Data |
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1da177e4 | 1 | /* |
1da177e4 LT |
2 | * Block device elevator/IO-scheduler. |
3 | * | |
4 | * Copyright (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE | |
5 | * | |
0fe23479 | 6 | * 30042000 Jens Axboe <axboe@kernel.dk> : |
1da177e4 LT |
7 | * |
8 | * Split the elevator a bit so that it is possible to choose a different | |
9 | * one or even write a new "plug in". There are three pieces: | |
10 | * - elevator_fn, inserts a new request in the queue list | |
11 | * - elevator_merge_fn, decides whether a new buffer can be merged with | |
12 | * an existing request | |
13 | * - elevator_dequeue_fn, called when a request is taken off the active list | |
14 | * | |
15 | * 20082000 Dave Jones <davej@suse.de> : | |
16 | * Removed tests for max-bomb-segments, which was breaking elvtune | |
17 | * when run without -bN | |
18 | * | |
19 | * Jens: | |
20 | * - Rework again to work with bio instead of buffer_heads | |
21 | * - loose bi_dev comparisons, partition handling is right now | |
22 | * - completely modularize elevator setup and teardown | |
23 | * | |
24 | */ | |
25 | #include <linux/kernel.h> | |
26 | #include <linux/fs.h> | |
27 | #include <linux/blkdev.h> | |
28 | #include <linux/elevator.h> | |
29 | #include <linux/bio.h> | |
1da177e4 LT |
30 | #include <linux/module.h> |
31 | #include <linux/slab.h> | |
32 | #include <linux/init.h> | |
33 | #include <linux/compiler.h> | |
2056a782 | 34 | #include <linux/blktrace_api.h> |
9817064b | 35 | #include <linux/hash.h> |
0835da67 | 36 | #include <linux/uaccess.h> |
1da177e4 | 37 | |
55782138 LZ |
38 | #include <trace/events/block.h> |
39 | ||
242f9dcb | 40 | #include "blk.h" |
72e06c25 | 41 | #include "blk-cgroup.h" |
242f9dcb | 42 | |
1da177e4 LT |
43 | static DEFINE_SPINLOCK(elv_list_lock); |
44 | static LIST_HEAD(elv_list); | |
45 | ||
9817064b JA |
46 | /* |
47 | * Merge hash stuff. | |
48 | */ | |
49 | static const int elv_hash_shift = 6; | |
50 | #define ELV_HASH_BLOCK(sec) ((sec) >> 3) | |
4eb166d9 JA |
51 | #define ELV_HASH_FN(sec) \ |
52 | (hash_long(ELV_HASH_BLOCK((sec)), elv_hash_shift)) | |
9817064b | 53 | #define ELV_HASH_ENTRIES (1 << elv_hash_shift) |
83096ebf | 54 | #define rq_hash_key(rq) (blk_rq_pos(rq) + blk_rq_sectors(rq)) |
9817064b | 55 | |
da775265 JA |
56 | /* |
57 | * Query io scheduler to see if the current process issuing bio may be | |
58 | * merged with rq. | |
59 | */ | |
60 | static int elv_iosched_allow_merge(struct request *rq, struct bio *bio) | |
61 | { | |
165125e1 | 62 | struct request_queue *q = rq->q; |
b374d18a | 63 | struct elevator_queue *e = q->elevator; |
da775265 | 64 | |
22f746e2 TH |
65 | if (e->type->ops.elevator_allow_merge_fn) |
66 | return e->type->ops.elevator_allow_merge_fn(q, rq, bio); | |
da775265 JA |
67 | |
68 | return 1; | |
69 | } | |
70 | ||
1da177e4 LT |
71 | /* |
72 | * can we safely merge with this request? | |
73 | */ | |
050c8ea8 | 74 | bool elv_rq_merge_ok(struct request *rq, struct bio *bio) |
1da177e4 | 75 | { |
050c8ea8 | 76 | if (!blk_rq_merge_ok(rq, bio)) |
7ba1ba12 MP |
77 | return 0; |
78 | ||
da775265 JA |
79 | if (!elv_iosched_allow_merge(rq, bio)) |
80 | return 0; | |
1da177e4 | 81 | |
da775265 | 82 | return 1; |
1da177e4 LT |
83 | } |
84 | EXPORT_SYMBOL(elv_rq_merge_ok); | |
85 | ||
1da177e4 LT |
86 | static struct elevator_type *elevator_find(const char *name) |
87 | { | |
a22b169d | 88 | struct elevator_type *e; |
1da177e4 | 89 | |
70cee26e | 90 | list_for_each_entry(e, &elv_list, list) { |
a22b169d VT |
91 | if (!strcmp(e->elevator_name, name)) |
92 | return e; | |
1da177e4 | 93 | } |
1da177e4 | 94 | |
a22b169d | 95 | return NULL; |
1da177e4 LT |
96 | } |
97 | ||
98 | static void elevator_put(struct elevator_type *e) | |
99 | { | |
100 | module_put(e->elevator_owner); | |
101 | } | |
102 | ||
103 | static struct elevator_type *elevator_get(const char *name) | |
104 | { | |
2824bc93 | 105 | struct elevator_type *e; |
1da177e4 | 106 | |
2a12dcd7 | 107 | spin_lock(&elv_list_lock); |
2824bc93 TH |
108 | |
109 | e = elevator_find(name); | |
e1640949 | 110 | if (!e) { |
e1640949 | 111 | spin_unlock(&elv_list_lock); |
490b94be | 112 | request_module("%s-iosched", name); |
e1640949 JA |
113 | spin_lock(&elv_list_lock); |
114 | e = elevator_find(name); | |
115 | } | |
116 | ||
2824bc93 TH |
117 | if (e && !try_module_get(e->elevator_owner)) |
118 | e = NULL; | |
119 | ||
2a12dcd7 | 120 | spin_unlock(&elv_list_lock); |
1da177e4 LT |
121 | |
122 | return e; | |
123 | } | |
124 | ||
484fc254 | 125 | static char chosen_elevator[ELV_NAME_MAX]; |
1da177e4 | 126 | |
5f003976 | 127 | static int __init elevator_setup(char *str) |
1da177e4 | 128 | { |
752a3b79 CE |
129 | /* |
130 | * Be backwards-compatible with previous kernels, so users | |
131 | * won't get the wrong elevator. | |
132 | */ | |
492af635 | 133 | strncpy(chosen_elevator, str, sizeof(chosen_elevator) - 1); |
9b41046c | 134 | return 1; |
1da177e4 LT |
135 | } |
136 | ||
137 | __setup("elevator=", elevator_setup); | |
138 | ||
bb813f4c TH |
139 | /* called during boot to load the elevator chosen by the elevator param */ |
140 | void __init load_default_elevator_module(void) | |
141 | { | |
142 | struct elevator_type *e; | |
143 | ||
144 | if (!chosen_elevator[0]) | |
145 | return; | |
146 | ||
147 | spin_lock(&elv_list_lock); | |
148 | e = elevator_find(chosen_elevator); | |
149 | spin_unlock(&elv_list_lock); | |
150 | ||
151 | if (!e) | |
152 | request_module("%s-iosched", chosen_elevator); | |
153 | } | |
154 | ||
3d1ab40f AV |
155 | static struct kobj_type elv_ktype; |
156 | ||
b374d18a | 157 | static struct elevator_queue *elevator_alloc(struct request_queue *q, |
165125e1 | 158 | struct elevator_type *e) |
3d1ab40f | 159 | { |
b374d18a | 160 | struct elevator_queue *eq; |
9817064b JA |
161 | int i; |
162 | ||
b374d18a | 163 | eq = kmalloc_node(sizeof(*eq), GFP_KERNEL | __GFP_ZERO, q->node); |
9817064b JA |
164 | if (unlikely(!eq)) |
165 | goto err; | |
166 | ||
22f746e2 | 167 | eq->type = e; |
f9cb074b | 168 | kobject_init(&eq->kobj, &elv_ktype); |
9817064b JA |
169 | mutex_init(&eq->sysfs_lock); |
170 | ||
b5deef90 JA |
171 | eq->hash = kmalloc_node(sizeof(struct hlist_head) * ELV_HASH_ENTRIES, |
172 | GFP_KERNEL, q->node); | |
9817064b JA |
173 | if (!eq->hash) |
174 | goto err; | |
175 | ||
176 | for (i = 0; i < ELV_HASH_ENTRIES; i++) | |
177 | INIT_HLIST_HEAD(&eq->hash[i]); | |
178 | ||
3d1ab40f | 179 | return eq; |
9817064b JA |
180 | err: |
181 | kfree(eq); | |
182 | elevator_put(e); | |
183 | return NULL; | |
3d1ab40f AV |
184 | } |
185 | ||
186 | static void elevator_release(struct kobject *kobj) | |
187 | { | |
b374d18a | 188 | struct elevator_queue *e; |
9817064b | 189 | |
b374d18a | 190 | e = container_of(kobj, struct elevator_queue, kobj); |
22f746e2 | 191 | elevator_put(e->type); |
9817064b | 192 | kfree(e->hash); |
3d1ab40f AV |
193 | kfree(e); |
194 | } | |
195 | ||
165125e1 | 196 | int elevator_init(struct request_queue *q, char *name) |
1da177e4 LT |
197 | { |
198 | struct elevator_type *e = NULL; | |
f8fc877d | 199 | int err; |
1da177e4 | 200 | |
1abec4fd MS |
201 | if (unlikely(q->elevator)) |
202 | return 0; | |
203 | ||
cb98fc8b TH |
204 | INIT_LIST_HEAD(&q->queue_head); |
205 | q->last_merge = NULL; | |
206 | q->end_sector = 0; | |
207 | q->boundary_rq = NULL; | |
cb98fc8b | 208 | |
4eb166d9 JA |
209 | if (name) { |
210 | e = elevator_get(name); | |
211 | if (!e) | |
212 | return -EINVAL; | |
213 | } | |
1da177e4 | 214 | |
4eb166d9 JA |
215 | if (!e && *chosen_elevator) { |
216 | e = elevator_get(chosen_elevator); | |
217 | if (!e) | |
218 | printk(KERN_ERR "I/O scheduler %s not found\n", | |
219 | chosen_elevator); | |
220 | } | |
248d5ca5 | 221 | |
4eb166d9 JA |
222 | if (!e) { |
223 | e = elevator_get(CONFIG_DEFAULT_IOSCHED); | |
224 | if (!e) { | |
225 | printk(KERN_ERR | |
226 | "Default I/O scheduler not found. " \ | |
227 | "Using noop.\n"); | |
228 | e = elevator_get("noop"); | |
229 | } | |
5f003976 ND |
230 | } |
231 | ||
5a5bafdc TH |
232 | q->elevator = elevator_alloc(q, e); |
233 | if (!q->elevator) | |
1da177e4 | 234 | return -ENOMEM; |
1da177e4 | 235 | |
b2fab5ac | 236 | err = e->ops.elevator_init_fn(q); |
f8fc877d | 237 | if (err) { |
5a5bafdc | 238 | kobject_put(&q->elevator->kobj); |
f8fc877d | 239 | return err; |
bc1c1169 | 240 | } |
1da177e4 | 241 | |
1abec4fd | 242 | return 0; |
1da177e4 | 243 | } |
2e662b65 JA |
244 | EXPORT_SYMBOL(elevator_init); |
245 | ||
b374d18a | 246 | void elevator_exit(struct elevator_queue *e) |
1da177e4 | 247 | { |
3d1ab40f | 248 | mutex_lock(&e->sysfs_lock); |
22f746e2 TH |
249 | if (e->type->ops.elevator_exit_fn) |
250 | e->type->ops.elevator_exit_fn(e); | |
3d1ab40f | 251 | mutex_unlock(&e->sysfs_lock); |
1da177e4 | 252 | |
3d1ab40f | 253 | kobject_put(&e->kobj); |
1da177e4 | 254 | } |
2e662b65 JA |
255 | EXPORT_SYMBOL(elevator_exit); |
256 | ||
9817064b JA |
257 | static inline void __elv_rqhash_del(struct request *rq) |
258 | { | |
259 | hlist_del_init(&rq->hash); | |
260 | } | |
261 | ||
165125e1 | 262 | static void elv_rqhash_del(struct request_queue *q, struct request *rq) |
9817064b JA |
263 | { |
264 | if (ELV_ON_HASH(rq)) | |
265 | __elv_rqhash_del(rq); | |
266 | } | |
267 | ||
165125e1 | 268 | static void elv_rqhash_add(struct request_queue *q, struct request *rq) |
9817064b | 269 | { |
b374d18a | 270 | struct elevator_queue *e = q->elevator; |
9817064b JA |
271 | |
272 | BUG_ON(ELV_ON_HASH(rq)); | |
273 | hlist_add_head(&rq->hash, &e->hash[ELV_HASH_FN(rq_hash_key(rq))]); | |
274 | } | |
275 | ||
165125e1 | 276 | static void elv_rqhash_reposition(struct request_queue *q, struct request *rq) |
9817064b JA |
277 | { |
278 | __elv_rqhash_del(rq); | |
279 | elv_rqhash_add(q, rq); | |
280 | } | |
281 | ||
165125e1 | 282 | static struct request *elv_rqhash_find(struct request_queue *q, sector_t offset) |
9817064b | 283 | { |
b374d18a | 284 | struct elevator_queue *e = q->elevator; |
9817064b JA |
285 | struct hlist_head *hash_list = &e->hash[ELV_HASH_FN(offset)]; |
286 | struct hlist_node *entry, *next; | |
287 | struct request *rq; | |
288 | ||
289 | hlist_for_each_entry_safe(rq, entry, next, hash_list, hash) { | |
290 | BUG_ON(!ELV_ON_HASH(rq)); | |
291 | ||
292 | if (unlikely(!rq_mergeable(rq))) { | |
293 | __elv_rqhash_del(rq); | |
294 | continue; | |
295 | } | |
296 | ||
297 | if (rq_hash_key(rq) == offset) | |
298 | return rq; | |
299 | } | |
300 | ||
301 | return NULL; | |
302 | } | |
303 | ||
2e662b65 JA |
304 | /* |
305 | * RB-tree support functions for inserting/lookup/removal of requests | |
306 | * in a sorted RB tree. | |
307 | */ | |
796d5116 | 308 | void elv_rb_add(struct rb_root *root, struct request *rq) |
2e662b65 JA |
309 | { |
310 | struct rb_node **p = &root->rb_node; | |
311 | struct rb_node *parent = NULL; | |
312 | struct request *__rq; | |
313 | ||
314 | while (*p) { | |
315 | parent = *p; | |
316 | __rq = rb_entry(parent, struct request, rb_node); | |
317 | ||
83096ebf | 318 | if (blk_rq_pos(rq) < blk_rq_pos(__rq)) |
2e662b65 | 319 | p = &(*p)->rb_left; |
796d5116 | 320 | else if (blk_rq_pos(rq) >= blk_rq_pos(__rq)) |
2e662b65 | 321 | p = &(*p)->rb_right; |
2e662b65 JA |
322 | } |
323 | ||
324 | rb_link_node(&rq->rb_node, parent, p); | |
325 | rb_insert_color(&rq->rb_node, root); | |
2e662b65 | 326 | } |
2e662b65 JA |
327 | EXPORT_SYMBOL(elv_rb_add); |
328 | ||
329 | void elv_rb_del(struct rb_root *root, struct request *rq) | |
330 | { | |
331 | BUG_ON(RB_EMPTY_NODE(&rq->rb_node)); | |
332 | rb_erase(&rq->rb_node, root); | |
333 | RB_CLEAR_NODE(&rq->rb_node); | |
334 | } | |
2e662b65 JA |
335 | EXPORT_SYMBOL(elv_rb_del); |
336 | ||
337 | struct request *elv_rb_find(struct rb_root *root, sector_t sector) | |
338 | { | |
339 | struct rb_node *n = root->rb_node; | |
340 | struct request *rq; | |
341 | ||
342 | while (n) { | |
343 | rq = rb_entry(n, struct request, rb_node); | |
344 | ||
83096ebf | 345 | if (sector < blk_rq_pos(rq)) |
2e662b65 | 346 | n = n->rb_left; |
83096ebf | 347 | else if (sector > blk_rq_pos(rq)) |
2e662b65 JA |
348 | n = n->rb_right; |
349 | else | |
350 | return rq; | |
351 | } | |
352 | ||
353 | return NULL; | |
354 | } | |
2e662b65 JA |
355 | EXPORT_SYMBOL(elv_rb_find); |
356 | ||
8922e16c TH |
357 | /* |
358 | * Insert rq into dispatch queue of q. Queue lock must be held on | |
dbe7f76d | 359 | * entry. rq is sort instead into the dispatch queue. To be used by |
2e662b65 | 360 | * specific elevators. |
8922e16c | 361 | */ |
165125e1 | 362 | void elv_dispatch_sort(struct request_queue *q, struct request *rq) |
8922e16c TH |
363 | { |
364 | sector_t boundary; | |
8922e16c | 365 | struct list_head *entry; |
4eb166d9 | 366 | int stop_flags; |
8922e16c | 367 | |
06b86245 TH |
368 | if (q->last_merge == rq) |
369 | q->last_merge = NULL; | |
9817064b JA |
370 | |
371 | elv_rqhash_del(q, rq); | |
372 | ||
15853af9 | 373 | q->nr_sorted--; |
06b86245 | 374 | |
1b47f531 | 375 | boundary = q->end_sector; |
02e031cb | 376 | stop_flags = REQ_SOFTBARRIER | REQ_STARTED; |
8922e16c TH |
377 | list_for_each_prev(entry, &q->queue_head) { |
378 | struct request *pos = list_entry_rq(entry); | |
379 | ||
33659ebb CH |
380 | if ((rq->cmd_flags & REQ_DISCARD) != |
381 | (pos->cmd_flags & REQ_DISCARD)) | |
e17fc0a1 | 382 | break; |
783660b2 JA |
383 | if (rq_data_dir(rq) != rq_data_dir(pos)) |
384 | break; | |
4eb166d9 | 385 | if (pos->cmd_flags & stop_flags) |
8922e16c | 386 | break; |
83096ebf TH |
387 | if (blk_rq_pos(rq) >= boundary) { |
388 | if (blk_rq_pos(pos) < boundary) | |
8922e16c TH |
389 | continue; |
390 | } else { | |
83096ebf | 391 | if (blk_rq_pos(pos) >= boundary) |
8922e16c TH |
392 | break; |
393 | } | |
83096ebf | 394 | if (blk_rq_pos(rq) >= blk_rq_pos(pos)) |
8922e16c TH |
395 | break; |
396 | } | |
397 | ||
398 | list_add(&rq->queuelist, entry); | |
399 | } | |
2e662b65 JA |
400 | EXPORT_SYMBOL(elv_dispatch_sort); |
401 | ||
9817064b | 402 | /* |
2e662b65 JA |
403 | * Insert rq into dispatch queue of q. Queue lock must be held on |
404 | * entry. rq is added to the back of the dispatch queue. To be used by | |
405 | * specific elevators. | |
9817064b JA |
406 | */ |
407 | void elv_dispatch_add_tail(struct request_queue *q, struct request *rq) | |
408 | { | |
409 | if (q->last_merge == rq) | |
410 | q->last_merge = NULL; | |
411 | ||
412 | elv_rqhash_del(q, rq); | |
413 | ||
414 | q->nr_sorted--; | |
415 | ||
416 | q->end_sector = rq_end_sector(rq); | |
417 | q->boundary_rq = rq; | |
418 | list_add_tail(&rq->queuelist, &q->queue_head); | |
419 | } | |
2e662b65 JA |
420 | EXPORT_SYMBOL(elv_dispatch_add_tail); |
421 | ||
165125e1 | 422 | int elv_merge(struct request_queue *q, struct request **req, struct bio *bio) |
1da177e4 | 423 | { |
b374d18a | 424 | struct elevator_queue *e = q->elevator; |
9817064b | 425 | struct request *__rq; |
06b86245 TH |
426 | int ret; |
427 | ||
488991e2 AB |
428 | /* |
429 | * Levels of merges: | |
430 | * nomerges: No merges at all attempted | |
431 | * noxmerges: Only simple one-hit cache try | |
432 | * merges: All merge tries attempted | |
433 | */ | |
434 | if (blk_queue_nomerges(q)) | |
435 | return ELEVATOR_NO_MERGE; | |
436 | ||
9817064b JA |
437 | /* |
438 | * First try one-hit cache. | |
439 | */ | |
050c8ea8 TH |
440 | if (q->last_merge && elv_rq_merge_ok(q->last_merge, bio)) { |
441 | ret = blk_try_merge(q->last_merge, bio); | |
06b86245 TH |
442 | if (ret != ELEVATOR_NO_MERGE) { |
443 | *req = q->last_merge; | |
444 | return ret; | |
445 | } | |
446 | } | |
1da177e4 | 447 | |
488991e2 | 448 | if (blk_queue_noxmerges(q)) |
ac9fafa1 AB |
449 | return ELEVATOR_NO_MERGE; |
450 | ||
9817064b JA |
451 | /* |
452 | * See if our hash lookup can find a potential backmerge. | |
453 | */ | |
454 | __rq = elv_rqhash_find(q, bio->bi_sector); | |
455 | if (__rq && elv_rq_merge_ok(__rq, bio)) { | |
456 | *req = __rq; | |
457 | return ELEVATOR_BACK_MERGE; | |
458 | } | |
459 | ||
22f746e2 TH |
460 | if (e->type->ops.elevator_merge_fn) |
461 | return e->type->ops.elevator_merge_fn(q, req, bio); | |
1da177e4 LT |
462 | |
463 | return ELEVATOR_NO_MERGE; | |
464 | } | |
465 | ||
5e84ea3a JA |
466 | /* |
467 | * Attempt to do an insertion back merge. Only check for the case where | |
468 | * we can append 'rq' to an existing request, so we can throw 'rq' away | |
469 | * afterwards. | |
470 | * | |
471 | * Returns true if we merged, false otherwise | |
472 | */ | |
473 | static bool elv_attempt_insert_merge(struct request_queue *q, | |
474 | struct request *rq) | |
475 | { | |
476 | struct request *__rq; | |
bee0393c | 477 | bool ret; |
5e84ea3a JA |
478 | |
479 | if (blk_queue_nomerges(q)) | |
480 | return false; | |
481 | ||
482 | /* | |
483 | * First try one-hit cache. | |
484 | */ | |
485 | if (q->last_merge && blk_attempt_req_merge(q, q->last_merge, rq)) | |
486 | return true; | |
487 | ||
488 | if (blk_queue_noxmerges(q)) | |
489 | return false; | |
490 | ||
bee0393c | 491 | ret = false; |
5e84ea3a JA |
492 | /* |
493 | * See if our hash lookup can find a potential backmerge. | |
494 | */ | |
bee0393c SL |
495 | while (1) { |
496 | __rq = elv_rqhash_find(q, blk_rq_pos(rq)); | |
497 | if (!__rq || !blk_attempt_req_merge(q, __rq, rq)) | |
498 | break; | |
499 | ||
500 | /* The merged request could be merged with others, try again */ | |
501 | ret = true; | |
502 | rq = __rq; | |
503 | } | |
27419322 | 504 | |
bee0393c | 505 | return ret; |
5e84ea3a JA |
506 | } |
507 | ||
165125e1 | 508 | void elv_merged_request(struct request_queue *q, struct request *rq, int type) |
1da177e4 | 509 | { |
b374d18a | 510 | struct elevator_queue *e = q->elevator; |
1da177e4 | 511 | |
22f746e2 TH |
512 | if (e->type->ops.elevator_merged_fn) |
513 | e->type->ops.elevator_merged_fn(q, rq, type); | |
06b86245 | 514 | |
2e662b65 JA |
515 | if (type == ELEVATOR_BACK_MERGE) |
516 | elv_rqhash_reposition(q, rq); | |
9817064b | 517 | |
06b86245 | 518 | q->last_merge = rq; |
1da177e4 LT |
519 | } |
520 | ||
165125e1 | 521 | void elv_merge_requests(struct request_queue *q, struct request *rq, |
1da177e4 LT |
522 | struct request *next) |
523 | { | |
b374d18a | 524 | struct elevator_queue *e = q->elevator; |
5e84ea3a | 525 | const int next_sorted = next->cmd_flags & REQ_SORTED; |
1da177e4 | 526 | |
22f746e2 TH |
527 | if (next_sorted && e->type->ops.elevator_merge_req_fn) |
528 | e->type->ops.elevator_merge_req_fn(q, rq, next); | |
06b86245 | 529 | |
9817064b | 530 | elv_rqhash_reposition(q, rq); |
9817064b | 531 | |
5e84ea3a JA |
532 | if (next_sorted) { |
533 | elv_rqhash_del(q, next); | |
534 | q->nr_sorted--; | |
535 | } | |
536 | ||
06b86245 | 537 | q->last_merge = rq; |
1da177e4 LT |
538 | } |
539 | ||
812d4026 DS |
540 | void elv_bio_merged(struct request_queue *q, struct request *rq, |
541 | struct bio *bio) | |
542 | { | |
543 | struct elevator_queue *e = q->elevator; | |
544 | ||
22f746e2 TH |
545 | if (e->type->ops.elevator_bio_merged_fn) |
546 | e->type->ops.elevator_bio_merged_fn(q, rq, bio); | |
812d4026 DS |
547 | } |
548 | ||
165125e1 | 549 | void elv_requeue_request(struct request_queue *q, struct request *rq) |
1da177e4 | 550 | { |
1da177e4 LT |
551 | /* |
552 | * it already went through dequeue, we need to decrement the | |
553 | * in_flight count again | |
554 | */ | |
8922e16c | 555 | if (blk_account_rq(rq)) { |
0a7ae2ff | 556 | q->in_flight[rq_is_sync(rq)]--; |
33659ebb | 557 | if (rq->cmd_flags & REQ_SORTED) |
cad97516 | 558 | elv_deactivate_rq(q, rq); |
8922e16c | 559 | } |
1da177e4 | 560 | |
4aff5e23 | 561 | rq->cmd_flags &= ~REQ_STARTED; |
1da177e4 | 562 | |
b710a480 | 563 | __elv_add_request(q, rq, ELEVATOR_INSERT_REQUEUE); |
1da177e4 LT |
564 | } |
565 | ||
26308eab | 566 | void elv_drain_elevator(struct request_queue *q) |
15853af9 TH |
567 | { |
568 | static int printed; | |
e3c78ca5 TH |
569 | |
570 | lockdep_assert_held(q->queue_lock); | |
571 | ||
22f746e2 | 572 | while (q->elevator->type->ops.elevator_dispatch_fn(q, 1)) |
15853af9 | 573 | ; |
e3c78ca5 | 574 | if (q->nr_sorted && printed++ < 10) { |
15853af9 TH |
575 | printk(KERN_ERR "%s: forced dispatching is broken " |
576 | "(nr_sorted=%u), please report this\n", | |
22f746e2 | 577 | q->elevator->type->elevator_name, q->nr_sorted); |
15853af9 TH |
578 | } |
579 | } | |
580 | ||
b710a480 | 581 | void __elv_add_request(struct request_queue *q, struct request *rq, int where) |
1da177e4 | 582 | { |
5f3ea37c | 583 | trace_block_rq_insert(q, rq); |
2056a782 | 584 | |
1da177e4 LT |
585 | rq->q = q; |
586 | ||
b710a480 JA |
587 | if (rq->cmd_flags & REQ_SOFTBARRIER) { |
588 | /* barriers are scheduling boundary, update end_sector */ | |
e2a60da7 | 589 | if (rq->cmd_type == REQ_TYPE_FS) { |
b710a480 JA |
590 | q->end_sector = rq_end_sector(rq); |
591 | q->boundary_rq = rq; | |
592 | } | |
593 | } else if (!(rq->cmd_flags & REQ_ELVPRIV) && | |
3aa72873 JA |
594 | (where == ELEVATOR_INSERT_SORT || |
595 | where == ELEVATOR_INSERT_SORT_MERGE)) | |
b710a480 JA |
596 | where = ELEVATOR_INSERT_BACK; |
597 | ||
8922e16c | 598 | switch (where) { |
28e7d184 | 599 | case ELEVATOR_INSERT_REQUEUE: |
8922e16c | 600 | case ELEVATOR_INSERT_FRONT: |
4aff5e23 | 601 | rq->cmd_flags |= REQ_SOFTBARRIER; |
8922e16c TH |
602 | list_add(&rq->queuelist, &q->queue_head); |
603 | break; | |
604 | ||
605 | case ELEVATOR_INSERT_BACK: | |
4aff5e23 | 606 | rq->cmd_flags |= REQ_SOFTBARRIER; |
15853af9 | 607 | elv_drain_elevator(q); |
8922e16c TH |
608 | list_add_tail(&rq->queuelist, &q->queue_head); |
609 | /* | |
610 | * We kick the queue here for the following reasons. | |
611 | * - The elevator might have returned NULL previously | |
612 | * to delay requests and returned them now. As the | |
613 | * queue wasn't empty before this request, ll_rw_blk | |
614 | * won't run the queue on return, resulting in hang. | |
615 | * - Usually, back inserted requests won't be merged | |
616 | * with anything. There's no point in delaying queue | |
617 | * processing. | |
618 | */ | |
24ecfbe2 | 619 | __blk_run_queue(q); |
8922e16c TH |
620 | break; |
621 | ||
5e84ea3a JA |
622 | case ELEVATOR_INSERT_SORT_MERGE: |
623 | /* | |
624 | * If we succeed in merging this request with one in the | |
625 | * queue already, we are done - rq has now been freed, | |
626 | * so no need to do anything further. | |
627 | */ | |
628 | if (elv_attempt_insert_merge(q, rq)) | |
629 | break; | |
8922e16c | 630 | case ELEVATOR_INSERT_SORT: |
e2a60da7 | 631 | BUG_ON(rq->cmd_type != REQ_TYPE_FS); |
4aff5e23 | 632 | rq->cmd_flags |= REQ_SORTED; |
15853af9 | 633 | q->nr_sorted++; |
9817064b JA |
634 | if (rq_mergeable(rq)) { |
635 | elv_rqhash_add(q, rq); | |
636 | if (!q->last_merge) | |
637 | q->last_merge = rq; | |
638 | } | |
639 | ||
ca23509f TH |
640 | /* |
641 | * Some ioscheds (cfq) run q->request_fn directly, so | |
642 | * rq cannot be accessed after calling | |
643 | * elevator_add_req_fn. | |
644 | */ | |
22f746e2 | 645 | q->elevator->type->ops.elevator_add_req_fn(q, rq); |
8922e16c TH |
646 | break; |
647 | ||
ae1b1539 TH |
648 | case ELEVATOR_INSERT_FLUSH: |
649 | rq->cmd_flags |= REQ_SOFTBARRIER; | |
650 | blk_insert_flush(rq); | |
651 | break; | |
8922e16c TH |
652 | default: |
653 | printk(KERN_ERR "%s: bad insertion point %d\n", | |
24c03d47 | 654 | __func__, where); |
8922e16c TH |
655 | BUG(); |
656 | } | |
1da177e4 | 657 | } |
2e662b65 JA |
658 | EXPORT_SYMBOL(__elv_add_request); |
659 | ||
7eaceacc | 660 | void elv_add_request(struct request_queue *q, struct request *rq, int where) |
1da177e4 LT |
661 | { |
662 | unsigned long flags; | |
663 | ||
664 | spin_lock_irqsave(q->queue_lock, flags); | |
7eaceacc | 665 | __elv_add_request(q, rq, where); |
1da177e4 LT |
666 | spin_unlock_irqrestore(q->queue_lock, flags); |
667 | } | |
2e662b65 JA |
668 | EXPORT_SYMBOL(elv_add_request); |
669 | ||
165125e1 | 670 | struct request *elv_latter_request(struct request_queue *q, struct request *rq) |
1da177e4 | 671 | { |
b374d18a | 672 | struct elevator_queue *e = q->elevator; |
1da177e4 | 673 | |
22f746e2 TH |
674 | if (e->type->ops.elevator_latter_req_fn) |
675 | return e->type->ops.elevator_latter_req_fn(q, rq); | |
1da177e4 LT |
676 | return NULL; |
677 | } | |
678 | ||
165125e1 | 679 | struct request *elv_former_request(struct request_queue *q, struct request *rq) |
1da177e4 | 680 | { |
b374d18a | 681 | struct elevator_queue *e = q->elevator; |
1da177e4 | 682 | |
22f746e2 TH |
683 | if (e->type->ops.elevator_former_req_fn) |
684 | return e->type->ops.elevator_former_req_fn(q, rq); | |
1da177e4 LT |
685 | return NULL; |
686 | } | |
687 | ||
852c788f TH |
688 | int elv_set_request(struct request_queue *q, struct request *rq, |
689 | struct bio *bio, gfp_t gfp_mask) | |
1da177e4 | 690 | { |
b374d18a | 691 | struct elevator_queue *e = q->elevator; |
1da177e4 | 692 | |
22f746e2 | 693 | if (e->type->ops.elevator_set_req_fn) |
852c788f | 694 | return e->type->ops.elevator_set_req_fn(q, rq, bio, gfp_mask); |
1da177e4 LT |
695 | return 0; |
696 | } | |
697 | ||
165125e1 | 698 | void elv_put_request(struct request_queue *q, struct request *rq) |
1da177e4 | 699 | { |
b374d18a | 700 | struct elevator_queue *e = q->elevator; |
1da177e4 | 701 | |
22f746e2 TH |
702 | if (e->type->ops.elevator_put_req_fn) |
703 | e->type->ops.elevator_put_req_fn(rq); | |
1da177e4 LT |
704 | } |
705 | ||
165125e1 | 706 | int elv_may_queue(struct request_queue *q, int rw) |
1da177e4 | 707 | { |
b374d18a | 708 | struct elevator_queue *e = q->elevator; |
1da177e4 | 709 | |
22f746e2 TH |
710 | if (e->type->ops.elevator_may_queue_fn) |
711 | return e->type->ops.elevator_may_queue_fn(q, rw); | |
1da177e4 LT |
712 | |
713 | return ELV_MQUEUE_MAY; | |
714 | } | |
715 | ||
11914a53 MA |
716 | void elv_abort_queue(struct request_queue *q) |
717 | { | |
718 | struct request *rq; | |
719 | ||
ae1b1539 TH |
720 | blk_abort_flushes(q); |
721 | ||
11914a53 MA |
722 | while (!list_empty(&q->queue_head)) { |
723 | rq = list_entry_rq(q->queue_head.next); | |
724 | rq->cmd_flags |= REQ_QUIET; | |
5f3ea37c | 725 | trace_block_rq_abort(q, rq); |
53c663ce KU |
726 | /* |
727 | * Mark this request as started so we don't trigger | |
728 | * any debug logic in the end I/O path. | |
729 | */ | |
730 | blk_start_request(rq); | |
40cbbb78 | 731 | __blk_end_request_all(rq, -EIO); |
11914a53 MA |
732 | } |
733 | } | |
734 | EXPORT_SYMBOL(elv_abort_queue); | |
735 | ||
165125e1 | 736 | void elv_completed_request(struct request_queue *q, struct request *rq) |
1da177e4 | 737 | { |
b374d18a | 738 | struct elevator_queue *e = q->elevator; |
1da177e4 LT |
739 | |
740 | /* | |
741 | * request is released from the driver, io must be done | |
742 | */ | |
8922e16c | 743 | if (blk_account_rq(rq)) { |
0a7ae2ff | 744 | q->in_flight[rq_is_sync(rq)]--; |
33659ebb | 745 | if ((rq->cmd_flags & REQ_SORTED) && |
22f746e2 TH |
746 | e->type->ops.elevator_completed_req_fn) |
747 | e->type->ops.elevator_completed_req_fn(q, rq); | |
1bc691d3 | 748 | } |
1da177e4 LT |
749 | } |
750 | ||
3d1ab40f AV |
751 | #define to_elv(atr) container_of((atr), struct elv_fs_entry, attr) |
752 | ||
753 | static ssize_t | |
754 | elv_attr_show(struct kobject *kobj, struct attribute *attr, char *page) | |
1da177e4 | 755 | { |
3d1ab40f | 756 | struct elv_fs_entry *entry = to_elv(attr); |
b374d18a | 757 | struct elevator_queue *e; |
3d1ab40f AV |
758 | ssize_t error; |
759 | ||
760 | if (!entry->show) | |
761 | return -EIO; | |
762 | ||
b374d18a | 763 | e = container_of(kobj, struct elevator_queue, kobj); |
3d1ab40f | 764 | mutex_lock(&e->sysfs_lock); |
22f746e2 | 765 | error = e->type ? entry->show(e, page) : -ENOENT; |
3d1ab40f AV |
766 | mutex_unlock(&e->sysfs_lock); |
767 | return error; | |
768 | } | |
1da177e4 | 769 | |
3d1ab40f AV |
770 | static ssize_t |
771 | elv_attr_store(struct kobject *kobj, struct attribute *attr, | |
772 | const char *page, size_t length) | |
773 | { | |
3d1ab40f | 774 | struct elv_fs_entry *entry = to_elv(attr); |
b374d18a | 775 | struct elevator_queue *e; |
3d1ab40f | 776 | ssize_t error; |
1da177e4 | 777 | |
3d1ab40f AV |
778 | if (!entry->store) |
779 | return -EIO; | |
1da177e4 | 780 | |
b374d18a | 781 | e = container_of(kobj, struct elevator_queue, kobj); |
3d1ab40f | 782 | mutex_lock(&e->sysfs_lock); |
22f746e2 | 783 | error = e->type ? entry->store(e, page, length) : -ENOENT; |
3d1ab40f AV |
784 | mutex_unlock(&e->sysfs_lock); |
785 | return error; | |
786 | } | |
787 | ||
52cf25d0 | 788 | static const struct sysfs_ops elv_sysfs_ops = { |
3d1ab40f AV |
789 | .show = elv_attr_show, |
790 | .store = elv_attr_store, | |
791 | }; | |
792 | ||
793 | static struct kobj_type elv_ktype = { | |
794 | .sysfs_ops = &elv_sysfs_ops, | |
795 | .release = elevator_release, | |
796 | }; | |
797 | ||
5a5bafdc | 798 | int elv_register_queue(struct request_queue *q) |
3d1ab40f | 799 | { |
5a5bafdc | 800 | struct elevator_queue *e = q->elevator; |
3d1ab40f AV |
801 | int error; |
802 | ||
b2d6db58 | 803 | error = kobject_add(&e->kobj, &q->kobj, "%s", "iosched"); |
3d1ab40f | 804 | if (!error) { |
22f746e2 | 805 | struct elv_fs_entry *attr = e->type->elevator_attrs; |
3d1ab40f | 806 | if (attr) { |
e572ec7e AV |
807 | while (attr->attr.name) { |
808 | if (sysfs_create_file(&e->kobj, &attr->attr)) | |
3d1ab40f | 809 | break; |
e572ec7e | 810 | attr++; |
3d1ab40f AV |
811 | } |
812 | } | |
813 | kobject_uevent(&e->kobj, KOBJ_ADD); | |
430c62fb | 814 | e->registered = 1; |
3d1ab40f AV |
815 | } |
816 | return error; | |
1da177e4 | 817 | } |
f8fc877d | 818 | EXPORT_SYMBOL(elv_register_queue); |
bc1c1169 | 819 | |
1da177e4 LT |
820 | void elv_unregister_queue(struct request_queue *q) |
821 | { | |
f8fc877d TH |
822 | if (q) { |
823 | struct elevator_queue *e = q->elevator; | |
824 | ||
825 | kobject_uevent(&e->kobj, KOBJ_REMOVE); | |
826 | kobject_del(&e->kobj); | |
827 | e->registered = 0; | |
828 | } | |
1da177e4 | 829 | } |
01effb0d | 830 | EXPORT_SYMBOL(elv_unregister_queue); |
1da177e4 | 831 | |
3d3c2379 | 832 | int elv_register(struct elevator_type *e) |
1da177e4 | 833 | { |
1ffb96c5 | 834 | char *def = ""; |
2a12dcd7 | 835 | |
3d3c2379 TH |
836 | /* create icq_cache if requested */ |
837 | if (e->icq_size) { | |
838 | if (WARN_ON(e->icq_size < sizeof(struct io_cq)) || | |
839 | WARN_ON(e->icq_align < __alignof__(struct io_cq))) | |
840 | return -EINVAL; | |
841 | ||
842 | snprintf(e->icq_cache_name, sizeof(e->icq_cache_name), | |
843 | "%s_io_cq", e->elevator_name); | |
844 | e->icq_cache = kmem_cache_create(e->icq_cache_name, e->icq_size, | |
845 | e->icq_align, 0, NULL); | |
846 | if (!e->icq_cache) | |
847 | return -ENOMEM; | |
848 | } | |
849 | ||
850 | /* register, don't allow duplicate names */ | |
2a12dcd7 | 851 | spin_lock(&elv_list_lock); |
3d3c2379 TH |
852 | if (elevator_find(e->elevator_name)) { |
853 | spin_unlock(&elv_list_lock); | |
854 | if (e->icq_cache) | |
855 | kmem_cache_destroy(e->icq_cache); | |
856 | return -EBUSY; | |
857 | } | |
1da177e4 | 858 | list_add_tail(&e->list, &elv_list); |
2a12dcd7 | 859 | spin_unlock(&elv_list_lock); |
1da177e4 | 860 | |
3d3c2379 | 861 | /* print pretty message */ |
5f003976 ND |
862 | if (!strcmp(e->elevator_name, chosen_elevator) || |
863 | (!*chosen_elevator && | |
864 | !strcmp(e->elevator_name, CONFIG_DEFAULT_IOSCHED))) | |
1ffb96c5 TV |
865 | def = " (default)"; |
866 | ||
4eb166d9 JA |
867 | printk(KERN_INFO "io scheduler %s registered%s\n", e->elevator_name, |
868 | def); | |
3d3c2379 | 869 | return 0; |
1da177e4 LT |
870 | } |
871 | EXPORT_SYMBOL_GPL(elv_register); | |
872 | ||
873 | void elv_unregister(struct elevator_type *e) | |
874 | { | |
3d3c2379 | 875 | /* unregister */ |
2a12dcd7 | 876 | spin_lock(&elv_list_lock); |
1da177e4 | 877 | list_del_init(&e->list); |
2a12dcd7 | 878 | spin_unlock(&elv_list_lock); |
3d3c2379 TH |
879 | |
880 | /* | |
881 | * Destroy icq_cache if it exists. icq's are RCU managed. Make | |
882 | * sure all RCU operations are complete before proceeding. | |
883 | */ | |
884 | if (e->icq_cache) { | |
885 | rcu_barrier(); | |
886 | kmem_cache_destroy(e->icq_cache); | |
887 | e->icq_cache = NULL; | |
888 | } | |
1da177e4 LT |
889 | } |
890 | EXPORT_SYMBOL_GPL(elv_unregister); | |
891 | ||
892 | /* | |
893 | * switch to new_e io scheduler. be careful not to introduce deadlocks - | |
894 | * we don't free the old io scheduler, before we have allocated what we | |
895 | * need for the new one. this way we have a chance of going back to the old | |
cb98fc8b | 896 | * one, if the new one fails init for some reason. |
1da177e4 | 897 | */ |
165125e1 | 898 | static int elevator_switch(struct request_queue *q, struct elevator_type *new_e) |
1da177e4 | 899 | { |
5a5bafdc TH |
900 | struct elevator_queue *old = q->elevator; |
901 | bool registered = old->registered; | |
e8989fae | 902 | int err; |
1da177e4 | 903 | |
5a5bafdc TH |
904 | /* |
905 | * Turn on BYPASS and drain all requests w/ elevator private data. | |
906 | * Block layer doesn't call into a quiesced elevator - all requests | |
907 | * are directly put on the dispatch list without elevator data | |
908 | * using INSERT_BACK. All requests have SOFTBARRIER set and no | |
909 | * merge happens either. | |
910 | */ | |
d732580b | 911 | blk_queue_bypass_start(q); |
cb98fc8b | 912 | |
5a5bafdc TH |
913 | /* unregister and clear all auxiliary data of the old elevator */ |
914 | if (registered) | |
f8fc877d | 915 | elv_unregister_queue(q); |
1da177e4 | 916 | |
f8fc877d | 917 | spin_lock_irq(q->queue_lock); |
7e5a8794 | 918 | ioc_clear_queue(q); |
f8fc877d TH |
919 | spin_unlock_irq(q->queue_lock); |
920 | ||
5a5bafdc TH |
921 | /* allocate, init and register new elevator */ |
922 | err = -ENOMEM; | |
923 | q->elevator = elevator_alloc(q, new_e); | |
924 | if (!q->elevator) | |
925 | goto fail_init; | |
926 | ||
b2fab5ac | 927 | err = new_e->ops.elevator_init_fn(q); |
5a5bafdc TH |
928 | if (err) { |
929 | kobject_put(&q->elevator->kobj); | |
930 | goto fail_init; | |
931 | } | |
932 | ||
933 | if (registered) { | |
934 | err = elv_register_queue(q); | |
935 | if (err) | |
936 | goto fail_register; | |
937 | } | |
938 | ||
939 | /* done, kill the old one and finish */ | |
940 | elevator_exit(old); | |
d732580b | 941 | blk_queue_bypass_end(q); |
75ad23bc | 942 | |
5a5bafdc | 943 | blk_add_trace_msg(q, "elv switch: %s", new_e->elevator_name); |
4722dc52 | 944 | |
5dd531a0 | 945 | return 0; |
1da177e4 LT |
946 | |
947 | fail_register: | |
5a5bafdc TH |
948 | elevator_exit(q->elevator); |
949 | fail_init: | |
950 | /* switch failed, restore and re-register old elevator */ | |
951 | q->elevator = old; | |
1da177e4 | 952 | elv_register_queue(q); |
d732580b | 953 | blk_queue_bypass_end(q); |
75ad23bc | 954 | |
5dd531a0 | 955 | return err; |
1da177e4 LT |
956 | } |
957 | ||
5dd531a0 JA |
958 | /* |
959 | * Switch this queue to the given IO scheduler. | |
960 | */ | |
961 | int elevator_change(struct request_queue *q, const char *name) | |
1da177e4 LT |
962 | { |
963 | char elevator_name[ELV_NAME_MAX]; | |
964 | struct elevator_type *e; | |
965 | ||
cd43e26f | 966 | if (!q->elevator) |
5dd531a0 | 967 | return -ENXIO; |
cd43e26f | 968 | |
ee2e992c | 969 | strlcpy(elevator_name, name, sizeof(elevator_name)); |
8c279598 | 970 | e = elevator_get(strstrip(elevator_name)); |
1da177e4 LT |
971 | if (!e) { |
972 | printk(KERN_ERR "elevator: type %s not found\n", elevator_name); | |
973 | return -EINVAL; | |
974 | } | |
975 | ||
22f746e2 | 976 | if (!strcmp(elevator_name, q->elevator->type->elevator_name)) { |
2ca7d93b | 977 | elevator_put(e); |
5dd531a0 | 978 | return 0; |
2ca7d93b | 979 | } |
1da177e4 | 980 | |
5dd531a0 JA |
981 | return elevator_switch(q, e); |
982 | } | |
983 | EXPORT_SYMBOL(elevator_change); | |
984 | ||
985 | ssize_t elv_iosched_store(struct request_queue *q, const char *name, | |
986 | size_t count) | |
987 | { | |
988 | int ret; | |
989 | ||
990 | if (!q->elevator) | |
991 | return count; | |
992 | ||
993 | ret = elevator_change(q, name); | |
994 | if (!ret) | |
995 | return count; | |
996 | ||
997 | printk(KERN_ERR "elevator: switch to %s failed\n", name); | |
998 | return ret; | |
1da177e4 LT |
999 | } |
1000 | ||
165125e1 | 1001 | ssize_t elv_iosched_show(struct request_queue *q, char *name) |
1da177e4 | 1002 | { |
b374d18a | 1003 | struct elevator_queue *e = q->elevator; |
cd43e26f | 1004 | struct elevator_type *elv; |
70cee26e | 1005 | struct elevator_type *__e; |
1da177e4 LT |
1006 | int len = 0; |
1007 | ||
e36f724b | 1008 | if (!q->elevator || !blk_queue_stackable(q)) |
cd43e26f MP |
1009 | return sprintf(name, "none\n"); |
1010 | ||
22f746e2 | 1011 | elv = e->type; |
cd43e26f | 1012 | |
2a12dcd7 | 1013 | spin_lock(&elv_list_lock); |
70cee26e | 1014 | list_for_each_entry(__e, &elv_list, list) { |
1da177e4 LT |
1015 | if (!strcmp(elv->elevator_name, __e->elevator_name)) |
1016 | len += sprintf(name+len, "[%s] ", elv->elevator_name); | |
1017 | else | |
1018 | len += sprintf(name+len, "%s ", __e->elevator_name); | |
1019 | } | |
2a12dcd7 | 1020 | spin_unlock(&elv_list_lock); |
1da177e4 LT |
1021 | |
1022 | len += sprintf(len+name, "\n"); | |
1023 | return len; | |
1024 | } | |
1025 | ||
165125e1 JA |
1026 | struct request *elv_rb_former_request(struct request_queue *q, |
1027 | struct request *rq) | |
2e662b65 JA |
1028 | { |
1029 | struct rb_node *rbprev = rb_prev(&rq->rb_node); | |
1030 | ||
1031 | if (rbprev) | |
1032 | return rb_entry_rq(rbprev); | |
1033 | ||
1034 | return NULL; | |
1035 | } | |
2e662b65 JA |
1036 | EXPORT_SYMBOL(elv_rb_former_request); |
1037 | ||
165125e1 JA |
1038 | struct request *elv_rb_latter_request(struct request_queue *q, |
1039 | struct request *rq) | |
2e662b65 JA |
1040 | { |
1041 | struct rb_node *rbnext = rb_next(&rq->rb_node); | |
1042 | ||
1043 | if (rbnext) | |
1044 | return rb_entry_rq(rbnext); | |
1045 | ||
1046 | return NULL; | |
1047 | } | |
2e662b65 | 1048 | EXPORT_SYMBOL(elv_rb_latter_request); |