2 * Block device elevator/IO-scheduler.
4 * Copyright (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE
6 * 30042000 Jens Axboe <axboe@kernel.dk> :
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
13 * - elevator_dequeue_fn, called when a request is taken off the active list
15 * 20082000 Dave Jones <davej@suse.de> :
16 * Removed tests for max-bomb-segments, which was breaking elvtune
17 * when run without -bN
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
25 #include <linux/kernel.h>
27 #include <linux/blkdev.h>
28 #include <linux/elevator.h>
29 #include <linux/bio.h>
30 #include <linux/module.h>
31 #include <linux/slab.h>
32 #include <linux/init.h>
33 #include <linux/compiler.h>
34 #include <linux/blktrace_api.h>
35 #include <linux/hash.h>
36 #include <linux/uaccess.h>
38 #include <trace/events/block.h>
41 #include "blk-cgroup.h"
43 static DEFINE_SPINLOCK(elv_list_lock);
44 static LIST_HEAD(elv_list);
49 #define rq_hash_key(rq) (blk_rq_pos(rq) + blk_rq_sectors(rq))
52 * Query io scheduler to see if the current process issuing bio may be
55 static int elv_iosched_allow_merge(struct request *rq, struct bio *bio)
57 struct request_queue *q = rq->q;
58 struct elevator_queue *e = q->elevator;
60 if (e->type->ops.elevator_allow_merge_fn)
61 return e->type->ops.elevator_allow_merge_fn(q, rq, bio);
67 * can we safely merge with this request?
69 bool elv_rq_merge_ok(struct request *rq, struct bio *bio)
71 if (!blk_rq_merge_ok(rq, bio))
74 if (!elv_iosched_allow_merge(rq, bio))
79 EXPORT_SYMBOL(elv_rq_merge_ok);
81 static struct elevator_type *elevator_find(const char *name)
83 struct elevator_type *e;
85 list_for_each_entry(e, &elv_list, list) {
86 if (!strcmp(e->elevator_name, name))
93 static void elevator_put(struct elevator_type *e)
95 module_put(e->elevator_owner);
98 static struct elevator_type *elevator_get(const char *name)
100 struct elevator_type *e;
102 spin_lock(&elv_list_lock);
104 e = elevator_find(name);
106 spin_unlock(&elv_list_lock);
107 request_module("%s-iosched", name);
108 spin_lock(&elv_list_lock);
109 e = elevator_find(name);
112 if (e && !try_module_get(e->elevator_owner))
115 spin_unlock(&elv_list_lock);
120 static char chosen_elevator[ELV_NAME_MAX];
122 static int __init elevator_setup(char *str)
125 * Be backwards-compatible with previous kernels, so users
126 * won't get the wrong elevator.
128 strncpy(chosen_elevator, str, sizeof(chosen_elevator) - 1);
132 __setup("elevator=", elevator_setup);
134 static struct kobj_type elv_ktype;
136 static struct elevator_queue *elevator_alloc(struct request_queue *q,
137 struct elevator_type *e)
139 struct elevator_queue *eq;
141 eq = kmalloc_node(sizeof(*eq), GFP_KERNEL | __GFP_ZERO, q->node);
146 kobject_init(&eq->kobj, &elv_ktype);
147 mutex_init(&eq->sysfs_lock);
157 static void elevator_release(struct kobject *kobj)
159 struct elevator_queue *e;
161 e = container_of(kobj, struct elevator_queue, kobj);
162 elevator_put(e->type);
166 int elevator_init(struct request_queue *q, char *name)
168 struct elevator_type *e = NULL;
171 if (unlikely(q->elevator))
174 INIT_LIST_HEAD(&q->queue_head);
175 q->last_merge = NULL;
177 q->boundary_rq = NULL;
180 e = elevator_get(name);
185 if (!e && *chosen_elevator) {
186 e = elevator_get(chosen_elevator);
188 printk(KERN_ERR "I/O scheduler %s not found\n",
193 e = elevator_get(CONFIG_DEFAULT_IOSCHED);
196 "Default I/O scheduler not found. " \
198 e = elevator_get("noop");
202 q->elevator = elevator_alloc(q, e);
206 err = e->ops.elevator_init_fn(q);
208 kobject_put(&q->elevator->kobj);
214 EXPORT_SYMBOL(elevator_init);
216 void elevator_exit(struct elevator_queue *e)
218 mutex_lock(&e->sysfs_lock);
219 if (e->type->ops.elevator_exit_fn)
220 e->type->ops.elevator_exit_fn(e);
221 mutex_unlock(&e->sysfs_lock);
223 kobject_put(&e->kobj);
225 EXPORT_SYMBOL(elevator_exit);
227 static inline void __elv_rqhash_del(struct request *rq)
232 static void elv_rqhash_del(struct request_queue *q, struct request *rq)
235 __elv_rqhash_del(rq);
238 static void elv_rqhash_add(struct request_queue *q, struct request *rq)
240 struct elevator_queue *e = q->elevator;
242 BUG_ON(ELV_ON_HASH(rq));
243 hash_add(e->hash, &rq->hash, rq_hash_key(rq));
246 static void elv_rqhash_reposition(struct request_queue *q, struct request *rq)
248 __elv_rqhash_del(rq);
249 elv_rqhash_add(q, rq);
252 static struct request *elv_rqhash_find(struct request_queue *q, sector_t offset)
254 struct elevator_queue *e = q->elevator;
255 struct hlist_node *entry, *next;
258 hash_for_each_possible_safe(e->hash, rq, entry, next, hash, offset) {
259 BUG_ON(!ELV_ON_HASH(rq));
261 if (unlikely(!rq_mergeable(rq))) {
262 __elv_rqhash_del(rq);
266 if (rq_hash_key(rq) == offset)
274 * RB-tree support functions for inserting/lookup/removal of requests
275 * in a sorted RB tree.
277 void elv_rb_add(struct rb_root *root, struct request *rq)
279 struct rb_node **p = &root->rb_node;
280 struct rb_node *parent = NULL;
281 struct request *__rq;
285 __rq = rb_entry(parent, struct request, rb_node);
287 if (blk_rq_pos(rq) < blk_rq_pos(__rq))
289 else if (blk_rq_pos(rq) >= blk_rq_pos(__rq))
293 rb_link_node(&rq->rb_node, parent, p);
294 rb_insert_color(&rq->rb_node, root);
296 EXPORT_SYMBOL(elv_rb_add);
298 void elv_rb_del(struct rb_root *root, struct request *rq)
300 BUG_ON(RB_EMPTY_NODE(&rq->rb_node));
301 rb_erase(&rq->rb_node, root);
302 RB_CLEAR_NODE(&rq->rb_node);
304 EXPORT_SYMBOL(elv_rb_del);
306 struct request *elv_rb_find(struct rb_root *root, sector_t sector)
308 struct rb_node *n = root->rb_node;
312 rq = rb_entry(n, struct request, rb_node);
314 if (sector < blk_rq_pos(rq))
316 else if (sector > blk_rq_pos(rq))
324 EXPORT_SYMBOL(elv_rb_find);
327 * Insert rq into dispatch queue of q. Queue lock must be held on
328 * entry. rq is sort instead into the dispatch queue. To be used by
329 * specific elevators.
331 void elv_dispatch_sort(struct request_queue *q, struct request *rq)
334 struct list_head *entry;
337 if (q->last_merge == rq)
338 q->last_merge = NULL;
340 elv_rqhash_del(q, rq);
344 boundary = q->end_sector;
345 stop_flags = REQ_SOFTBARRIER | REQ_STARTED;
346 list_for_each_prev(entry, &q->queue_head) {
347 struct request *pos = list_entry_rq(entry);
349 if ((rq->cmd_flags & REQ_DISCARD) !=
350 (pos->cmd_flags & REQ_DISCARD))
352 if (rq_data_dir(rq) != rq_data_dir(pos))
354 if (pos->cmd_flags & stop_flags)
356 if (blk_rq_pos(rq) >= boundary) {
357 if (blk_rq_pos(pos) < boundary)
360 if (blk_rq_pos(pos) >= boundary)
363 if (blk_rq_pos(rq) >= blk_rq_pos(pos))
367 list_add(&rq->queuelist, entry);
369 EXPORT_SYMBOL(elv_dispatch_sort);
372 * Insert rq into dispatch queue of q. Queue lock must be held on
373 * entry. rq is added to the back of the dispatch queue. To be used by
374 * specific elevators.
376 void elv_dispatch_add_tail(struct request_queue *q, struct request *rq)
378 if (q->last_merge == rq)
379 q->last_merge = NULL;
381 elv_rqhash_del(q, rq);
385 q->end_sector = rq_end_sector(rq);
387 list_add_tail(&rq->queuelist, &q->queue_head);
389 EXPORT_SYMBOL(elv_dispatch_add_tail);
391 int elv_merge(struct request_queue *q, struct request **req, struct bio *bio)
393 struct elevator_queue *e = q->elevator;
394 struct request *__rq;
399 * nomerges: No merges at all attempted
400 * noxmerges: Only simple one-hit cache try
401 * merges: All merge tries attempted
403 if (blk_queue_nomerges(q))
404 return ELEVATOR_NO_MERGE;
407 * First try one-hit cache.
409 if (q->last_merge && elv_rq_merge_ok(q->last_merge, bio)) {
410 ret = blk_try_merge(q->last_merge, bio);
411 if (ret != ELEVATOR_NO_MERGE) {
412 *req = q->last_merge;
417 if (blk_queue_noxmerges(q))
418 return ELEVATOR_NO_MERGE;
421 * See if our hash lookup can find a potential backmerge.
423 __rq = elv_rqhash_find(q, bio->bi_sector);
424 if (__rq && elv_rq_merge_ok(__rq, bio)) {
426 return ELEVATOR_BACK_MERGE;
429 if (e->type->ops.elevator_merge_fn)
430 return e->type->ops.elevator_merge_fn(q, req, bio);
432 return ELEVATOR_NO_MERGE;
436 * Attempt to do an insertion back merge. Only check for the case where
437 * we can append 'rq' to an existing request, so we can throw 'rq' away
440 * Returns true if we merged, false otherwise
442 static bool elv_attempt_insert_merge(struct request_queue *q,
445 struct request *__rq;
448 if (blk_queue_nomerges(q))
452 * First try one-hit cache.
454 if (q->last_merge && blk_attempt_req_merge(q, q->last_merge, rq))
457 if (blk_queue_noxmerges(q))
462 * See if our hash lookup can find a potential backmerge.
465 __rq = elv_rqhash_find(q, blk_rq_pos(rq));
466 if (!__rq || !blk_attempt_req_merge(q, __rq, rq))
469 /* The merged request could be merged with others, try again */
477 void elv_merged_request(struct request_queue *q, struct request *rq, int type)
479 struct elevator_queue *e = q->elevator;
481 if (e->type->ops.elevator_merged_fn)
482 e->type->ops.elevator_merged_fn(q, rq, type);
484 if (type == ELEVATOR_BACK_MERGE)
485 elv_rqhash_reposition(q, rq);
490 void elv_merge_requests(struct request_queue *q, struct request *rq,
491 struct request *next)
493 struct elevator_queue *e = q->elevator;
494 const int next_sorted = next->cmd_flags & REQ_SORTED;
496 if (next_sorted && e->type->ops.elevator_merge_req_fn)
497 e->type->ops.elevator_merge_req_fn(q, rq, next);
499 elv_rqhash_reposition(q, rq);
502 elv_rqhash_del(q, next);
509 void elv_bio_merged(struct request_queue *q, struct request *rq,
512 struct elevator_queue *e = q->elevator;
514 if (e->type->ops.elevator_bio_merged_fn)
515 e->type->ops.elevator_bio_merged_fn(q, rq, bio);
518 void elv_requeue_request(struct request_queue *q, struct request *rq)
521 * it already went through dequeue, we need to decrement the
522 * in_flight count again
524 if (blk_account_rq(rq)) {
525 q->in_flight[rq_is_sync(rq)]--;
526 if (rq->cmd_flags & REQ_SORTED)
527 elv_deactivate_rq(q, rq);
530 rq->cmd_flags &= ~REQ_STARTED;
532 __elv_add_request(q, rq, ELEVATOR_INSERT_REQUEUE);
535 void elv_drain_elevator(struct request_queue *q)
539 lockdep_assert_held(q->queue_lock);
541 while (q->elevator->type->ops.elevator_dispatch_fn(q, 1))
543 if (q->nr_sorted && printed++ < 10) {
544 printk(KERN_ERR "%s: forced dispatching is broken "
545 "(nr_sorted=%u), please report this\n",
546 q->elevator->type->elevator_name, q->nr_sorted);
550 void __elv_add_request(struct request_queue *q, struct request *rq, int where)
552 trace_block_rq_insert(q, rq);
556 if (rq->cmd_flags & REQ_SOFTBARRIER) {
557 /* barriers are scheduling boundary, update end_sector */
558 if (rq->cmd_type == REQ_TYPE_FS) {
559 q->end_sector = rq_end_sector(rq);
562 } else if (!(rq->cmd_flags & REQ_ELVPRIV) &&
563 (where == ELEVATOR_INSERT_SORT ||
564 where == ELEVATOR_INSERT_SORT_MERGE))
565 where = ELEVATOR_INSERT_BACK;
568 case ELEVATOR_INSERT_REQUEUE:
569 case ELEVATOR_INSERT_FRONT:
570 rq->cmd_flags |= REQ_SOFTBARRIER;
571 list_add(&rq->queuelist, &q->queue_head);
574 case ELEVATOR_INSERT_BACK:
575 rq->cmd_flags |= REQ_SOFTBARRIER;
576 elv_drain_elevator(q);
577 list_add_tail(&rq->queuelist, &q->queue_head);
579 * We kick the queue here for the following reasons.
580 * - The elevator might have returned NULL previously
581 * to delay requests and returned them now. As the
582 * queue wasn't empty before this request, ll_rw_blk
583 * won't run the queue on return, resulting in hang.
584 * - Usually, back inserted requests won't be merged
585 * with anything. There's no point in delaying queue
591 case ELEVATOR_INSERT_SORT_MERGE:
593 * If we succeed in merging this request with one in the
594 * queue already, we are done - rq has now been freed,
595 * so no need to do anything further.
597 if (elv_attempt_insert_merge(q, rq))
599 case ELEVATOR_INSERT_SORT:
600 BUG_ON(rq->cmd_type != REQ_TYPE_FS);
601 rq->cmd_flags |= REQ_SORTED;
603 if (rq_mergeable(rq)) {
604 elv_rqhash_add(q, rq);
610 * Some ioscheds (cfq) run q->request_fn directly, so
611 * rq cannot be accessed after calling
612 * elevator_add_req_fn.
614 q->elevator->type->ops.elevator_add_req_fn(q, rq);
617 case ELEVATOR_INSERT_FLUSH:
618 rq->cmd_flags |= REQ_SOFTBARRIER;
619 blk_insert_flush(rq);
622 printk(KERN_ERR "%s: bad insertion point %d\n",
627 EXPORT_SYMBOL(__elv_add_request);
629 void elv_add_request(struct request_queue *q, struct request *rq, int where)
633 spin_lock_irqsave(q->queue_lock, flags);
634 __elv_add_request(q, rq, where);
635 spin_unlock_irqrestore(q->queue_lock, flags);
637 EXPORT_SYMBOL(elv_add_request);
639 struct request *elv_latter_request(struct request_queue *q, struct request *rq)
641 struct elevator_queue *e = q->elevator;
643 if (e->type->ops.elevator_latter_req_fn)
644 return e->type->ops.elevator_latter_req_fn(q, rq);
648 struct request *elv_former_request(struct request_queue *q, struct request *rq)
650 struct elevator_queue *e = q->elevator;
652 if (e->type->ops.elevator_former_req_fn)
653 return e->type->ops.elevator_former_req_fn(q, rq);
657 int elv_set_request(struct request_queue *q, struct request *rq,
658 struct bio *bio, gfp_t gfp_mask)
660 struct elevator_queue *e = q->elevator;
662 if (e->type->ops.elevator_set_req_fn)
663 return e->type->ops.elevator_set_req_fn(q, rq, bio, gfp_mask);
667 void elv_put_request(struct request_queue *q, struct request *rq)
669 struct elevator_queue *e = q->elevator;
671 if (e->type->ops.elevator_put_req_fn)
672 e->type->ops.elevator_put_req_fn(rq);
675 int elv_may_queue(struct request_queue *q, int rw)
677 struct elevator_queue *e = q->elevator;
679 if (e->type->ops.elevator_may_queue_fn)
680 return e->type->ops.elevator_may_queue_fn(q, rw);
682 return ELV_MQUEUE_MAY;
685 void elv_abort_queue(struct request_queue *q)
689 blk_abort_flushes(q);
691 while (!list_empty(&q->queue_head)) {
692 rq = list_entry_rq(q->queue_head.next);
693 rq->cmd_flags |= REQ_QUIET;
694 trace_block_rq_abort(q, rq);
696 * Mark this request as started so we don't trigger
697 * any debug logic in the end I/O path.
699 blk_start_request(rq);
700 __blk_end_request_all(rq, -EIO);
703 EXPORT_SYMBOL(elv_abort_queue);
705 void elv_completed_request(struct request_queue *q, struct request *rq)
707 struct elevator_queue *e = q->elevator;
710 * request is released from the driver, io must be done
712 if (blk_account_rq(rq)) {
713 q->in_flight[rq_is_sync(rq)]--;
714 if ((rq->cmd_flags & REQ_SORTED) &&
715 e->type->ops.elevator_completed_req_fn)
716 e->type->ops.elevator_completed_req_fn(q, rq);
720 #define to_elv(atr) container_of((atr), struct elv_fs_entry, attr)
723 elv_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
725 struct elv_fs_entry *entry = to_elv(attr);
726 struct elevator_queue *e;
732 e = container_of(kobj, struct elevator_queue, kobj);
733 mutex_lock(&e->sysfs_lock);
734 error = e->type ? entry->show(e, page) : -ENOENT;
735 mutex_unlock(&e->sysfs_lock);
740 elv_attr_store(struct kobject *kobj, struct attribute *attr,
741 const char *page, size_t length)
743 struct elv_fs_entry *entry = to_elv(attr);
744 struct elevator_queue *e;
750 e = container_of(kobj, struct elevator_queue, kobj);
751 mutex_lock(&e->sysfs_lock);
752 error = e->type ? entry->store(e, page, length) : -ENOENT;
753 mutex_unlock(&e->sysfs_lock);
757 static const struct sysfs_ops elv_sysfs_ops = {
758 .show = elv_attr_show,
759 .store = elv_attr_store,
762 static struct kobj_type elv_ktype = {
763 .sysfs_ops = &elv_sysfs_ops,
764 .release = elevator_release,
767 int elv_register_queue(struct request_queue *q)
769 struct elevator_queue *e = q->elevator;
772 error = kobject_add(&e->kobj, &q->kobj, "%s", "iosched");
774 struct elv_fs_entry *attr = e->type->elevator_attrs;
776 while (attr->attr.name) {
777 if (sysfs_create_file(&e->kobj, &attr->attr))
782 kobject_uevent(&e->kobj, KOBJ_ADD);
787 EXPORT_SYMBOL(elv_register_queue);
789 void elv_unregister_queue(struct request_queue *q)
792 struct elevator_queue *e = q->elevator;
794 kobject_uevent(&e->kobj, KOBJ_REMOVE);
795 kobject_del(&e->kobj);
799 EXPORT_SYMBOL(elv_unregister_queue);
801 int elv_register(struct elevator_type *e)
805 /* create icq_cache if requested */
807 if (WARN_ON(e->icq_size < sizeof(struct io_cq)) ||
808 WARN_ON(e->icq_align < __alignof__(struct io_cq)))
811 snprintf(e->icq_cache_name, sizeof(e->icq_cache_name),
812 "%s_io_cq", e->elevator_name);
813 e->icq_cache = kmem_cache_create(e->icq_cache_name, e->icq_size,
814 e->icq_align, 0, NULL);
819 /* register, don't allow duplicate names */
820 spin_lock(&elv_list_lock);
821 if (elevator_find(e->elevator_name)) {
822 spin_unlock(&elv_list_lock);
824 kmem_cache_destroy(e->icq_cache);
827 list_add_tail(&e->list, &elv_list);
828 spin_unlock(&elv_list_lock);
830 /* print pretty message */
831 if (!strcmp(e->elevator_name, chosen_elevator) ||
832 (!*chosen_elevator &&
833 !strcmp(e->elevator_name, CONFIG_DEFAULT_IOSCHED)))
836 printk(KERN_INFO "io scheduler %s registered%s\n", e->elevator_name,
840 EXPORT_SYMBOL_GPL(elv_register);
842 void elv_unregister(struct elevator_type *e)
845 spin_lock(&elv_list_lock);
846 list_del_init(&e->list);
847 spin_unlock(&elv_list_lock);
850 * Destroy icq_cache if it exists. icq's are RCU managed. Make
851 * sure all RCU operations are complete before proceeding.
855 kmem_cache_destroy(e->icq_cache);
859 EXPORT_SYMBOL_GPL(elv_unregister);
862 * switch to new_e io scheduler. be careful not to introduce deadlocks -
863 * we don't free the old io scheduler, before we have allocated what we
864 * need for the new one. this way we have a chance of going back to the old
865 * one, if the new one fails init for some reason.
867 static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
869 struct elevator_queue *old = q->elevator;
870 bool registered = old->registered;
874 * Turn on BYPASS and drain all requests w/ elevator private data.
875 * Block layer doesn't call into a quiesced elevator - all requests
876 * are directly put on the dispatch list without elevator data
877 * using INSERT_BACK. All requests have SOFTBARRIER set and no
878 * merge happens either.
880 blk_queue_bypass_start(q);
882 /* unregister and clear all auxiliary data of the old elevator */
884 elv_unregister_queue(q);
886 spin_lock_irq(q->queue_lock);
888 spin_unlock_irq(q->queue_lock);
890 /* allocate, init and register new elevator */
892 q->elevator = elevator_alloc(q, new_e);
896 err = new_e->ops.elevator_init_fn(q);
898 kobject_put(&q->elevator->kobj);
903 err = elv_register_queue(q);
908 /* done, kill the old one and finish */
910 blk_queue_bypass_end(q);
912 blk_add_trace_msg(q, "elv switch: %s", new_e->elevator_name);
917 elevator_exit(q->elevator);
919 /* switch failed, restore and re-register old elevator */
921 elv_register_queue(q);
922 blk_queue_bypass_end(q);
928 * Switch this queue to the given IO scheduler.
930 int elevator_change(struct request_queue *q, const char *name)
932 char elevator_name[ELV_NAME_MAX];
933 struct elevator_type *e;
938 strlcpy(elevator_name, name, sizeof(elevator_name));
939 e = elevator_get(strstrip(elevator_name));
941 printk(KERN_ERR "elevator: type %s not found\n", elevator_name);
945 if (!strcmp(elevator_name, q->elevator->type->elevator_name)) {
950 return elevator_switch(q, e);
952 EXPORT_SYMBOL(elevator_change);
954 ssize_t elv_iosched_store(struct request_queue *q, const char *name,
962 ret = elevator_change(q, name);
966 printk(KERN_ERR "elevator: switch to %s failed\n", name);
970 ssize_t elv_iosched_show(struct request_queue *q, char *name)
972 struct elevator_queue *e = q->elevator;
973 struct elevator_type *elv;
974 struct elevator_type *__e;
977 if (!q->elevator || !blk_queue_stackable(q))
978 return sprintf(name, "none\n");
982 spin_lock(&elv_list_lock);
983 list_for_each_entry(__e, &elv_list, list) {
984 if (!strcmp(elv->elevator_name, __e->elevator_name))
985 len += sprintf(name+len, "[%s] ", elv->elevator_name);
987 len += sprintf(name+len, "%s ", __e->elevator_name);
989 spin_unlock(&elv_list_lock);
991 len += sprintf(len+name, "\n");
995 struct request *elv_rb_former_request(struct request_queue *q,
998 struct rb_node *rbprev = rb_prev(&rq->rb_node);
1001 return rb_entry_rq(rbprev);
1005 EXPORT_SYMBOL(elv_rb_former_request);
1007 struct request *elv_rb_latter_request(struct request_queue *q,
1010 struct rb_node *rbnext = rb_next(&rq->rb_node);
1013 return rb_entry_rq(rbnext);
1017 EXPORT_SYMBOL(elv_rb_latter_request);