/drivers/block/elevator.c

https://bitbucket.org/evzijst/gittest · C · 705 lines · 448 code · 134 blank · 123 comment · 95 complexity · ed45ec46a53e02a41fd5592ecc1d0c83 MD5 · raw file

  1. /*
  2. * linux/drivers/block/elevator.c
  3. *
  4. * Block device elevator/IO-scheduler.
  5. *
  6. * Copyright (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE
  7. *
  8. * 30042000 Jens Axboe <axboe@suse.de> :
  9. *
  10. * Split the elevator a bit so that it is possible to choose a different
  11. * one or even write a new "plug in". There are three pieces:
  12. * - elevator_fn, inserts a new request in the queue list
  13. * - elevator_merge_fn, decides whether a new buffer can be merged with
  14. * an existing request
  15. * - elevator_dequeue_fn, called when a request is taken off the active list
  16. *
  17. * 20082000 Dave Jones <davej@suse.de> :
  18. * Removed tests for max-bomb-segments, which was breaking elvtune
  19. * when run without -bN
  20. *
  21. * Jens:
  22. * - Rework again to work with bio instead of buffer_heads
  23. * - loose bi_dev comparisons, partition handling is right now
  24. * - completely modularize elevator setup and teardown
  25. *
  26. */
  27. #include <linux/kernel.h>
  28. #include <linux/fs.h>
  29. #include <linux/blkdev.h>
  30. #include <linux/elevator.h>
  31. #include <linux/bio.h>
  32. #include <linux/config.h>
  33. #include <linux/module.h>
  34. #include <linux/slab.h>
  35. #include <linux/init.h>
  36. #include <linux/compiler.h>
  37. #include <asm/uaccess.h>
  38. static DEFINE_SPINLOCK(elv_list_lock);
  39. static LIST_HEAD(elv_list);
  40. /*
  41. * can we safely merge with this request?
  42. */
  43. inline int elv_rq_merge_ok(struct request *rq, struct bio *bio)
  44. {
  45. if (!rq_mergeable(rq))
  46. return 0;
  47. /*
  48. * different data direction or already started, don't merge
  49. */
  50. if (bio_data_dir(bio) != rq_data_dir(rq))
  51. return 0;
  52. /*
  53. * same device and no special stuff set, merge is ok
  54. */
  55. if (rq->rq_disk == bio->bi_bdev->bd_disk &&
  56. !rq->waiting && !rq->special)
  57. return 1;
  58. return 0;
  59. }
  60. EXPORT_SYMBOL(elv_rq_merge_ok);
  61. inline int elv_try_merge(struct request *__rq, struct bio *bio)
  62. {
  63. int ret = ELEVATOR_NO_MERGE;
  64. /*
  65. * we can merge and sequence is ok, check if it's possible
  66. */
  67. if (elv_rq_merge_ok(__rq, bio)) {
  68. if (__rq->sector + __rq->nr_sectors == bio->bi_sector)
  69. ret = ELEVATOR_BACK_MERGE;
  70. else if (__rq->sector - bio_sectors(bio) == bio->bi_sector)
  71. ret = ELEVATOR_FRONT_MERGE;
  72. }
  73. return ret;
  74. }
  75. EXPORT_SYMBOL(elv_try_merge);
  76. inline int elv_try_last_merge(request_queue_t *q, struct bio *bio)
  77. {
  78. if (q->last_merge)
  79. return elv_try_merge(q->last_merge, bio);
  80. return ELEVATOR_NO_MERGE;
  81. }
  82. EXPORT_SYMBOL(elv_try_last_merge);
  83. static struct elevator_type *elevator_find(const char *name)
  84. {
  85. struct elevator_type *e = NULL;
  86. struct list_head *entry;
  87. spin_lock_irq(&elv_list_lock);
  88. list_for_each(entry, &elv_list) {
  89. struct elevator_type *__e;
  90. __e = list_entry(entry, struct elevator_type, list);
  91. if (!strcmp(__e->elevator_name, name)) {
  92. e = __e;
  93. break;
  94. }
  95. }
  96. spin_unlock_irq(&elv_list_lock);
  97. return e;
  98. }
  99. static void elevator_put(struct elevator_type *e)
  100. {
  101. module_put(e->elevator_owner);
  102. }
  103. static struct elevator_type *elevator_get(const char *name)
  104. {
  105. struct elevator_type *e = elevator_find(name);
  106. if (!e)
  107. return NULL;
  108. if (!try_module_get(e->elevator_owner))
  109. return NULL;
  110. return e;
  111. }
  112. static int elevator_attach(request_queue_t *q, struct elevator_type *e,
  113. struct elevator_queue *eq)
  114. {
  115. int ret = 0;
  116. memset(eq, 0, sizeof(*eq));
  117. eq->ops = &e->ops;
  118. eq->elevator_type = e;
  119. INIT_LIST_HEAD(&q->queue_head);
  120. q->last_merge = NULL;
  121. q->elevator = eq;
  122. if (eq->ops->elevator_init_fn)
  123. ret = eq->ops->elevator_init_fn(q, eq);
  124. return ret;
  125. }
  126. static char chosen_elevator[16];
  127. static void elevator_setup_default(void)
  128. {
  129. /*
  130. * check if default is set and exists
  131. */
  132. if (chosen_elevator[0] && elevator_find(chosen_elevator))
  133. return;
  134. #if defined(CONFIG_IOSCHED_AS)
  135. strcpy(chosen_elevator, "anticipatory");
  136. #elif defined(CONFIG_IOSCHED_DEADLINE)
  137. strcpy(chosen_elevator, "deadline");
  138. #elif defined(CONFIG_IOSCHED_CFQ)
  139. strcpy(chosen_elevator, "cfq");
  140. #elif defined(CONFIG_IOSCHED_NOOP)
  141. strcpy(chosen_elevator, "noop");
  142. #else
  143. #error "You must build at least 1 IO scheduler into the kernel"
  144. #endif
  145. }
  146. static int __init elevator_setup(char *str)
  147. {
  148. strncpy(chosen_elevator, str, sizeof(chosen_elevator) - 1);
  149. return 0;
  150. }
  151. __setup("elevator=", elevator_setup);
  152. int elevator_init(request_queue_t *q, char *name)
  153. {
  154. struct elevator_type *e = NULL;
  155. struct elevator_queue *eq;
  156. int ret = 0;
  157. elevator_setup_default();
  158. if (!name)
  159. name = chosen_elevator;
  160. e = elevator_get(name);
  161. if (!e)
  162. return -EINVAL;
  163. eq = kmalloc(sizeof(struct elevator_queue), GFP_KERNEL);
  164. if (!eq) {
  165. elevator_put(e->elevator_type);
  166. return -ENOMEM;
  167. }
  168. ret = elevator_attach(q, e, eq);
  169. if (ret) {
  170. kfree(eq);
  171. elevator_put(e->elevator_type);
  172. }
  173. return ret;
  174. }
  175. void elevator_exit(elevator_t *e)
  176. {
  177. if (e->ops->elevator_exit_fn)
  178. e->ops->elevator_exit_fn(e);
  179. elevator_put(e->elevator_type);
  180. e->elevator_type = NULL;
  181. kfree(e);
  182. }
  183. static int elevator_global_init(void)
  184. {
  185. return 0;
  186. }
  187. int elv_merge(request_queue_t *q, struct request **req, struct bio *bio)
  188. {
  189. elevator_t *e = q->elevator;
  190. if (e->ops->elevator_merge_fn)
  191. return e->ops->elevator_merge_fn(q, req, bio);
  192. return ELEVATOR_NO_MERGE;
  193. }
  194. void elv_merged_request(request_queue_t *q, struct request *rq)
  195. {
  196. elevator_t *e = q->elevator;
  197. if (e->ops->elevator_merged_fn)
  198. e->ops->elevator_merged_fn(q, rq);
  199. }
  200. void elv_merge_requests(request_queue_t *q, struct request *rq,
  201. struct request *next)
  202. {
  203. elevator_t *e = q->elevator;
  204. if (q->last_merge == next)
  205. q->last_merge = NULL;
  206. if (e->ops->elevator_merge_req_fn)
  207. e->ops->elevator_merge_req_fn(q, rq, next);
  208. }
  209. /*
  210. * For careful internal use by the block layer. Essentially the same as
  211. * a requeue in that it tells the io scheduler that this request is not
  212. * active in the driver or hardware anymore, but we don't want the request
  213. * added back to the scheduler. Function is not exported.
  214. */
  215. void elv_deactivate_request(request_queue_t *q, struct request *rq)
  216. {
  217. elevator_t *e = q->elevator;
  218. /*
  219. * it already went through dequeue, we need to decrement the
  220. * in_flight count again
  221. */
  222. if (blk_account_rq(rq))
  223. q->in_flight--;
  224. rq->flags &= ~REQ_STARTED;
  225. if (e->ops->elevator_deactivate_req_fn)
  226. e->ops->elevator_deactivate_req_fn(q, rq);
  227. }
  228. void elv_requeue_request(request_queue_t *q, struct request *rq)
  229. {
  230. elv_deactivate_request(q, rq);
  231. /*
  232. * if this is the flush, requeue the original instead and drop the flush
  233. */
  234. if (rq->flags & REQ_BAR_FLUSH) {
  235. clear_bit(QUEUE_FLAG_FLUSH, &q->queue_flags);
  236. rq = rq->end_io_data;
  237. }
  238. /*
  239. * if iosched has an explicit requeue hook, then use that. otherwise
  240. * just put the request at the front of the queue
  241. */
  242. if (q->elevator->ops->elevator_requeue_req_fn)
  243. q->elevator->ops->elevator_requeue_req_fn(q, rq);
  244. else
  245. __elv_add_request(q, rq, ELEVATOR_INSERT_FRONT, 0);
  246. }
  247. void __elv_add_request(request_queue_t *q, struct request *rq, int where,
  248. int plug)
  249. {
  250. /*
  251. * barriers implicitly indicate back insertion
  252. */
  253. if (rq->flags & (REQ_SOFTBARRIER | REQ_HARDBARRIER) &&
  254. where == ELEVATOR_INSERT_SORT)
  255. where = ELEVATOR_INSERT_BACK;
  256. if (plug)
  257. blk_plug_device(q);
  258. rq->q = q;
  259. if (!test_bit(QUEUE_FLAG_DRAIN, &q->queue_flags)) {
  260. q->elevator->ops->elevator_add_req_fn(q, rq, where);
  261. if (blk_queue_plugged(q)) {
  262. int nrq = q->rq.count[READ] + q->rq.count[WRITE]
  263. - q->in_flight;
  264. if (nrq == q->unplug_thresh)
  265. __generic_unplug_device(q);
  266. }
  267. } else
  268. /*
  269. * if drain is set, store the request "locally". when the drain
  270. * is finished, the requests will be handed ordered to the io
  271. * scheduler
  272. */
  273. list_add_tail(&rq->queuelist, &q->drain_list);
  274. }
  275. void elv_add_request(request_queue_t *q, struct request *rq, int where,
  276. int plug)
  277. {
  278. unsigned long flags;
  279. spin_lock_irqsave(q->queue_lock, flags);
  280. __elv_add_request(q, rq, where, plug);
  281. spin_unlock_irqrestore(q->queue_lock, flags);
  282. }
  283. static inline struct request *__elv_next_request(request_queue_t *q)
  284. {
  285. struct request *rq = q->elevator->ops->elevator_next_req_fn(q);
  286. /*
  287. * if this is a barrier write and the device has to issue a
  288. * flush sequence to support it, check how far we are
  289. */
  290. if (rq && blk_fs_request(rq) && blk_barrier_rq(rq)) {
  291. BUG_ON(q->ordered == QUEUE_ORDERED_NONE);
  292. if (q->ordered == QUEUE_ORDERED_FLUSH &&
  293. !blk_barrier_preflush(rq))
  294. rq = blk_start_pre_flush(q, rq);
  295. }
  296. return rq;
  297. }
  298. struct request *elv_next_request(request_queue_t *q)
  299. {
  300. struct request *rq;
  301. int ret;
  302. while ((rq = __elv_next_request(q)) != NULL) {
  303. /*
  304. * just mark as started even if we don't start it, a request
  305. * that has been delayed should not be passed by new incoming
  306. * requests
  307. */
  308. rq->flags |= REQ_STARTED;
  309. if (rq == q->last_merge)
  310. q->last_merge = NULL;
  311. if ((rq->flags & REQ_DONTPREP) || !q->prep_rq_fn)
  312. break;
  313. ret = q->prep_rq_fn(q, rq);
  314. if (ret == BLKPREP_OK) {
  315. break;
  316. } else if (ret == BLKPREP_DEFER) {
  317. rq = NULL;
  318. break;
  319. } else if (ret == BLKPREP_KILL) {
  320. int nr_bytes = rq->hard_nr_sectors << 9;
  321. if (!nr_bytes)
  322. nr_bytes = rq->data_len;
  323. blkdev_dequeue_request(rq);
  324. rq->flags |= REQ_QUIET;
  325. end_that_request_chunk(rq, 0, nr_bytes);
  326. end_that_request_last(rq);
  327. } else {
  328. printk(KERN_ERR "%s: bad return=%d\n", __FUNCTION__,
  329. ret);
  330. break;
  331. }
  332. }
  333. return rq;
  334. }
  335. void elv_remove_request(request_queue_t *q, struct request *rq)
  336. {
  337. elevator_t *e = q->elevator;
  338. /*
  339. * the time frame between a request being removed from the lists
  340. * and to it is freed is accounted as io that is in progress at
  341. * the driver side. note that we only account requests that the
  342. * driver has seen (REQ_STARTED set), to avoid false accounting
  343. * for request-request merges
  344. */
  345. if (blk_account_rq(rq))
  346. q->in_flight++;
  347. /*
  348. * the main clearing point for q->last_merge is on retrieval of
  349. * request by driver (it calls elv_next_request()), but it _can_
  350. * also happen here if a request is added to the queue but later
  351. * deleted without ever being given to driver (merged with another
  352. * request).
  353. */
  354. if (rq == q->last_merge)
  355. q->last_merge = NULL;
  356. if (e->ops->elevator_remove_req_fn)
  357. e->ops->elevator_remove_req_fn(q, rq);
  358. }
  359. int elv_queue_empty(request_queue_t *q)
  360. {
  361. elevator_t *e = q->elevator;
  362. if (e->ops->elevator_queue_empty_fn)
  363. return e->ops->elevator_queue_empty_fn(q);
  364. return list_empty(&q->queue_head);
  365. }
  366. struct request *elv_latter_request(request_queue_t *q, struct request *rq)
  367. {
  368. struct list_head *next;
  369. elevator_t *e = q->elevator;
  370. if (e->ops->elevator_latter_req_fn)
  371. return e->ops->elevator_latter_req_fn(q, rq);
  372. next = rq->queuelist.next;
  373. if (next != &q->queue_head && next != &rq->queuelist)
  374. return list_entry_rq(next);
  375. return NULL;
  376. }
  377. struct request *elv_former_request(request_queue_t *q, struct request *rq)
  378. {
  379. struct list_head *prev;
  380. elevator_t *e = q->elevator;
  381. if (e->ops->elevator_former_req_fn)
  382. return e->ops->elevator_former_req_fn(q, rq);
  383. prev = rq->queuelist.prev;
  384. if (prev != &q->queue_head && prev != &rq->queuelist)
  385. return list_entry_rq(prev);
  386. return NULL;
  387. }
  388. int elv_set_request(request_queue_t *q, struct request *rq, int gfp_mask)
  389. {
  390. elevator_t *e = q->elevator;
  391. if (e->ops->elevator_set_req_fn)
  392. return e->ops->elevator_set_req_fn(q, rq, gfp_mask);
  393. rq->elevator_private = NULL;
  394. return 0;
  395. }
  396. void elv_put_request(request_queue_t *q, struct request *rq)
  397. {
  398. elevator_t *e = q->elevator;
  399. if (e->ops->elevator_put_req_fn)
  400. e->ops->elevator_put_req_fn(q, rq);
  401. }
  402. int elv_may_queue(request_queue_t *q, int rw)
  403. {
  404. elevator_t *e = q->elevator;
  405. if (e->ops->elevator_may_queue_fn)
  406. return e->ops->elevator_may_queue_fn(q, rw);
  407. return ELV_MQUEUE_MAY;
  408. }
  409. void elv_completed_request(request_queue_t *q, struct request *rq)
  410. {
  411. elevator_t *e = q->elevator;
  412. /*
  413. * request is released from the driver, io must be done
  414. */
  415. if (blk_account_rq(rq))
  416. q->in_flight--;
  417. if (e->ops->elevator_completed_req_fn)
  418. e->ops->elevator_completed_req_fn(q, rq);
  419. }
  420. int elv_register_queue(struct request_queue *q)
  421. {
  422. elevator_t *e = q->elevator;
  423. e->kobj.parent = kobject_get(&q->kobj);
  424. if (!e->kobj.parent)
  425. return -EBUSY;
  426. snprintf(e->kobj.name, KOBJ_NAME_LEN, "%s", "iosched");
  427. e->kobj.ktype = e->elevator_type->elevator_ktype;
  428. return kobject_register(&e->kobj);
  429. }
  430. void elv_unregister_queue(struct request_queue *q)
  431. {
  432. if (q) {
  433. elevator_t *e = q->elevator;
  434. kobject_unregister(&e->kobj);
  435. kobject_put(&q->kobj);
  436. }
  437. }
  438. int elv_register(struct elevator_type *e)
  439. {
  440. if (elevator_find(e->elevator_name))
  441. BUG();
  442. spin_lock_irq(&elv_list_lock);
  443. list_add_tail(&e->list, &elv_list);
  444. spin_unlock_irq(&elv_list_lock);
  445. printk(KERN_INFO "io scheduler %s registered", e->elevator_name);
  446. if (!strcmp(e->elevator_name, chosen_elevator))
  447. printk(" (default)");
  448. printk("\n");
  449. return 0;
  450. }
  451. EXPORT_SYMBOL_GPL(elv_register);
  452. void elv_unregister(struct elevator_type *e)
  453. {
  454. spin_lock_irq(&elv_list_lock);
  455. list_del_init(&e->list);
  456. spin_unlock_irq(&elv_list_lock);
  457. }
  458. EXPORT_SYMBOL_GPL(elv_unregister);
  459. /*
  460. * switch to new_e io scheduler. be careful not to introduce deadlocks -
  461. * we don't free the old io scheduler, before we have allocated what we
  462. * need for the new one. this way we have a chance of going back to the old
  463. * one, if the new one fails init for some reason. we also do an intermediate
  464. * switch to noop to ensure safety with stack-allocated requests, since they
  465. * don't originate from the block layer allocator. noop is safe here, because
  466. * it never needs to touch the elevator itself for completion events. DRAIN
  467. * flags will make sure we don't touch it for additions either.
  468. */
  469. static void elevator_switch(request_queue_t *q, struct elevator_type *new_e)
  470. {
  471. elevator_t *e = kmalloc(sizeof(elevator_t), GFP_KERNEL);
  472. struct elevator_type *noop_elevator = NULL;
  473. elevator_t *old_elevator;
  474. if (!e)
  475. goto error;
  476. /*
  477. * first step, drain requests from the block freelist
  478. */
  479. blk_wait_queue_drained(q, 0);
  480. /*
  481. * unregister old elevator data
  482. */
  483. elv_unregister_queue(q);
  484. old_elevator = q->elevator;
  485. /*
  486. * next step, switch to noop since it uses no private rq structures
  487. * and doesn't allocate any memory for anything. then wait for any
  488. * non-fs requests in-flight
  489. */
  490. noop_elevator = elevator_get("noop");
  491. spin_lock_irq(q->queue_lock);
  492. elevator_attach(q, noop_elevator, e);
  493. spin_unlock_irq(q->queue_lock);
  494. blk_wait_queue_drained(q, 1);
  495. /*
  496. * attach and start new elevator
  497. */
  498. if (elevator_attach(q, new_e, e))
  499. goto fail;
  500. if (elv_register_queue(q))
  501. goto fail_register;
  502. /*
  503. * finally exit old elevator and start queue again
  504. */
  505. elevator_exit(old_elevator);
  506. blk_finish_queue_drain(q);
  507. elevator_put(noop_elevator);
  508. return;
  509. fail_register:
  510. /*
  511. * switch failed, exit the new io scheduler and reattach the old
  512. * one again (along with re-adding the sysfs dir)
  513. */
  514. elevator_exit(e);
  515. fail:
  516. q->elevator = old_elevator;
  517. elv_register_queue(q);
  518. blk_finish_queue_drain(q);
  519. error:
  520. if (noop_elevator)
  521. elevator_put(noop_elevator);
  522. elevator_put(new_e);
  523. printk(KERN_ERR "elevator: switch to %s failed\n",new_e->elevator_name);
  524. }
  525. ssize_t elv_iosched_store(request_queue_t *q, const char *name, size_t count)
  526. {
  527. char elevator_name[ELV_NAME_MAX];
  528. struct elevator_type *e;
  529. memset(elevator_name, 0, sizeof(elevator_name));
  530. strncpy(elevator_name, name, sizeof(elevator_name));
  531. if (elevator_name[strlen(elevator_name) - 1] == '\n')
  532. elevator_name[strlen(elevator_name) - 1] = '\0';
  533. e = elevator_get(elevator_name);
  534. if (!e) {
  535. printk(KERN_ERR "elevator: type %s not found\n", elevator_name);
  536. return -EINVAL;
  537. }
  538. if (!strcmp(elevator_name, q->elevator->elevator_type->elevator_name))
  539. return count;
  540. elevator_switch(q, e);
  541. return count;
  542. }
  543. ssize_t elv_iosched_show(request_queue_t *q, char *name)
  544. {
  545. elevator_t *e = q->elevator;
  546. struct elevator_type *elv = e->elevator_type;
  547. struct list_head *entry;
  548. int len = 0;
  549. spin_lock_irq(q->queue_lock);
  550. list_for_each(entry, &elv_list) {
  551. struct elevator_type *__e;
  552. __e = list_entry(entry, struct elevator_type, list);
  553. if (!strcmp(elv->elevator_name, __e->elevator_name))
  554. len += sprintf(name+len, "[%s] ", elv->elevator_name);
  555. else
  556. len += sprintf(name+len, "%s ", __e->elevator_name);
  557. }
  558. spin_unlock_irq(q->queue_lock);
  559. len += sprintf(len+name, "\n");
  560. return len;
  561. }
  562. module_init(elevator_global_init);
  563. EXPORT_SYMBOL(elv_add_request);
  564. EXPORT_SYMBOL(__elv_add_request);
  565. EXPORT_SYMBOL(elv_requeue_request);
  566. EXPORT_SYMBOL(elv_next_request);
  567. EXPORT_SYMBOL(elv_remove_request);
  568. EXPORT_SYMBOL(elv_queue_empty);
  569. EXPORT_SYMBOL(elv_completed_request);
  570. EXPORT_SYMBOL(elevator_exit);
  571. EXPORT_SYMBOL(elevator_init);