/* * Block device elevator/IO-scheduler. * * Copyright (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE * * 30042000 Jens Axboe <axboe@kernel.dk> : * * Split the elevator a bit so that it is possible to choose a different * one or even write a new "plug in". There are three pieces: * - elevator_fn, inserts a new request in the queue list * - elevator_merge_fn, decides whether a new buffer can be merged with * an existing request * - elevator_dequeue_fn, called when a request is taken off the active list * * 20082000 Dave Jones <davej@suse.de> : * Removed tests for max-bomb-segments, which was breaking elvtune * when run without -bN * * Jens: * - Rework again to work with bio instead of buffer_heads * - loose bi_dev comparisons, partition handling is right now * - completely modularize elevator setup and teardown * */ #include <linux/kernel.h> #include <linux/fs.h> #include <linux/blkdev.h> #include <linux/elevator.h> #include <linux/bio.h> #include <linux/module.h> #include <linux/slab.h> #include <linux/init.h> #include <linux/compiler.h> #include <linux/blktrace_api.h> #include <linux/hash.h> #include <linux/uaccess.h> #include <trace/events/block.h> #include "blk.h" #include "blk-cgroup.h" static DEFINE_SPINLOCK(elv_list_lock); static LIST_HEAD(elv_list); /* * Merge hash stuff. */ static const int elv_hash_shift = 6; #define ELV_HASH_BLOCK(sec) ((sec) >> 3) #define ELV_HASH_FN(sec) \ (hash_long(ELV_HASH_BLOCK((sec)), elv_hash_shift)) #define ELV_HASH_ENTRIES (1 << elv_hash_shift) #define rq_hash_key(rq) (blk_rq_pos(rq) + blk_rq_sectors(rq)) /* * Query io scheduler to see if the current process issuing bio may be * merged with rq. */ static int elv_iosched_allow_merge(struct request *rq, struct bio *bio) { struct request_queue *q = rq->q; struct elevator_queue *e = q->elevator; if (e->type->ops.elevator_allow_merge_fn) return e->type->ops.elevator_allow_merge_fn(q, rq, bio); return 1; } /* * can we safely merge with this request? */ bool elv_rq_merge_ok(struct request *rq, struct bio *bio) { if (!blk_rq_merge_ok(rq, bio)) return 0; if (!elv_iosched_allow_merge(rq, bio)) return 0; return 1; } EXPORT_SYMBOL(elv_rq_merge_ok); static struct elevator_type *elevator_find(const char *name) { struct elevator_type *e; list_for_each_entry(e, &elv_list, list) { if (!strcmp(e->elevator_name, name)) return e; } return NULL; } static void elevator_put(struct elevator_type *e) { module_put(e->elevator_owner); } static struct elevator_type *elevator_get(const char *name) { struct elevator_type *e; spin_lock(&elv_list_lock); e = elevator_find(name); if (!e) { spin_unlock(&elv_list_lock); request_module("%s-iosched", name); spin_lock(&elv_list_lock); e = elevator_find(name); } if (e && !try_module_get(e->elevator_owner)) e = NULL; spin_unlock(&elv_list_lock); return e; } static char chosen_elevator[ELV_NAME_MAX]; static int __init elevator_setup(char *str) { /* * Be backwards-compatible with previous kernels, so users * won't get the wrong elevator. */ strncpy(chosen_elevator, str, sizeof(chosen_elevator) - 1); return 1; } __setup("elevator=", elevator_setup); static struct kobj_type elv_ktype; static struct elevator_queue *elevator_alloc(struct request_queue *q, struct elevator_type *e) { struct elevator_queue *eq; int i; eq = kmalloc_node(sizeof(*eq), GFP_KERNEL | __GFP_ZERO, q->node); if (unlikely(!eq)) goto err; eq->type = e; kobject_init(&eq->kobj, &elv_ktype); mutex_init(&eq->sysfs_lock); eq->hash = kmalloc_node(sizeof(struct hlist_head) * ELV_HASH_ENTRIES, GFP_KERNEL, q->node); if (!eq->hash) goto err; for (i = 0; i < ELV_HASH_ENTRIES; i++) INIT_HLIST_HEAD(&eq->hash[i]); return eq; err: kfree(eq); elevator_put(e); return NULL; } static void elevator_release(struct kobject *kobj) { struct elevator_queue *e; e = container_of(kobj, struct elevator_queue, kobj); elevator_put(e->type); kfree(e->hash); kfree(e); } int elevator_init(struct request_queue *q, char *name) { struct elevator_type *e = NULL; int err; if (unlikely(q->elevator)) return 0; INIT_LIST_HEAD(&q->queue_head); q->last_merge = NULL; q->end_sector = 0; q->boundary_rq = NULL; if (name) { e = elevator_get(name); if (!e) return -EINVAL; } if (!e && *chosen_elevator) { e = elevator_get(chosen_elevator); if (!e) printk(KERN_ERR "I/O scheduler %s not found\n", chosen_elevator); } if (!e) { e = elevator_get(CONFIG_DEFAULT_IOSCHED); if (!e) { printk(KERN_ERR "Default I/O scheduler not found. " \ "Using noop.\n"); e = elevator_get("noop"); } } q->elevator = elevator_alloc(q, e); if (!q->elevator) return -ENOMEM; err = e->ops.elevator_init_fn(q); if (err) { kobject_put(&q->elevator->kobj); return err; } return 0; } EXPORT_SYMBOL(elevator_init); void elevator_exit(struct elevator_queue *e) { mutex_lock(&e->sysfs_lock); if (e->type->ops.elevator_exit_fn) e->type->ops.elevator_exit_fn(e); mutex_unlock(&e->sysfs_lock); kobject_put(&e->kobj); } EXPORT_SYMBOL(elevator_exit); static inline void __elv_rqhash_del(struct request *rq) { hlist_del_init(&rq->hash); } static void elv_rqhash_del(struct request_queue *q, struct request *rq) { if (ELV_ON_HASH(rq)) __elv_rqhash_del(rq); } static void elv_rqhash_add(struct request_queue *q, struct request *rq) { struct elevator_queue *e = q->elevator; BUG_ON(ELV_ON_HASH(rq)); hlist_add_head(&rq->hash, &e->hash[ELV_HASH_FN(rq_hash_key(rq))]); } static void elv_rqhash_reposition(struct request_queue *q, struct request *rq) { __elv_rqhash_del(rq); elv_rqhash_add(q, rq); } static struct request *elv_rqhash_find(struct request_queue *q, sector_t offset) { struct elevator_queue *e = q->elevator; struct hlist_head *hash_list = &e->hash[ELV_HASH_FN(offset)]; struct hlist_node *entry, *next; struct request *rq; hlist_for_each_entry_safe(rq, entry, next, hash_list, hash) { BUG_ON(!ELV_ON_HASH(rq)); if (unlikely(!rq_mergeable(rq))) { __elv_rqhash_del(rq); continue; } if (rq_hash_key(rq) == offset) return rq; } return NULL; } /* * RB-tree support functions for inserting/lookup/removal of requests * in a sorted RB tree. */ void elv_rb_add(struct rb_root *root, struct request *rq) { struct rb_node **p = &root->rb_node; struct rb_node *parent = NULL; struct request *__rq; while (*p) { parent = *p; __rq = rb_entry(parent, struct request, rb_node); if (blk_rq_pos(rq) < blk_rq_pos(__rq)) p = &(*p)->rb_left; else if (blk_rq_pos(rq) >= blk_rq_pos(__rq)) p = &(*p)->rb_right; } rb_link_node(&rq->rb_node, parent, p); rb_insert_color(&rq->rb_node, root); } EXPORT_SYMBOL(elv_rb_add); void elv_rb_del(struct rb_root *root, struct request *rq) { BUG_ON(RB_EMPTY_NODE(&rq->rb_node)); rb_erase(&rq->rb_node, root); RB_CLEAR_NODE(&rq->rb_node); } EXPORT_SYMBOL(elv_rb_del); struct request *elv_rb_find(struct rb_root *root, sector_t sector) { struct rb_node *n = root->rb_node; struct request *rq; while (n) { rq = rb_entry(n, struct request, rb_node); if (sector < blk_rq_pos(rq)) n = n->rb_left; else if (sector > blk_rq_pos(rq)) n = n->rb_right; else return rq; } return NULL; } EXPORT_SYMBOL(elv_rb_find); /* * Insert rq into dispatch queue of q. Queue lock must be held on * entry. rq is sort instead into the dispatch queue. To be used by * specific elevators. */ void elv_dispatch_sort(struct request_queue *q, struct request *rq) { sector_t boundary; struct list_head *entry; int stop_flags; if (q->last_merge == rq) q->last_merge = NULL; elv_rqhash_del(q, rq); q->nr_sorted--; boundary = q->end_sector; stop_flags = REQ_SOFTBARRIER | REQ_STARTED; list_for_each_prev(entry, &q->queue_head) { struct request *pos = list_entry_rq(entry); if ((rq->cmd_flags & REQ_DISCARD) != (pos->cmd_flags & REQ_DISCARD)) break; if (rq_data_dir(rq) != rq_data_dir(pos)) break; if (pos->cmd_flags & stop_flags) break; if (blk_rq_pos(rq) >= boundary) { if (blk_rq_pos(pos) < boundary) continue; } else { if (blk_rq_pos(pos) >= boundary) break; } if (blk_rq_pos(rq) >= blk_rq_pos(pos)) break; } list_add(&rq->queuelist, entry); } EXPORT_SYMBOL(elv_dispatch_sort); /* * Insert rq into dispatch queue of q. Queue lock must be held on * entry. rq is added to the back of the dispatch queue. To be used by * specific elevators. */ void elv_dispatch_add_tail(struct request_queue *q, struct request *rq) { if (q->last_merge == rq) q->last_merge = NULL; elv_rqhash_del(q, rq); q->nr_sorted--; q->end_sector = rq_end_sector(rq); q->boundary_rq = rq; list_add_tail(&rq->queuelist, &q->queue_head); } EXPORT_SYMBOL(elv_dispatch_add_tail); int elv_merge(struct request_queue *q, struct request **req, struct bio *bio) { struct elevator_queue *e = q->elevator; struct request *__rq; int ret; /* * Levels of merges: * nomerges: No merges at all attempted * noxmerges: Only simple one-hit cache try * merges: All merge tries attempted */ if (blk_queue_nomerges(q)) return ELEVATOR_NO_MERGE; /* * First try one-hit cache. */ if (q->last_merge && elv_rq_merge_ok(q->last_merge, bio)) { ret = blk_try_merge(q->last_merge, bio); if (ret != ELEVATOR_NO_MERGE) { *req = q->last_merge; return ret; } } if (blk_queue_noxmerges(q)) return ELEVATOR_NO_MERGE; /* * See if our hash lookup can find a potential backmerge. */ __rq = elv_rqhash_find(q, bio->bi_sector); if (__rq && elv_rq_merge_ok(__rq, bio)) { *req = __rq; return ELEVATOR_BACK_MERGE; } if (e->type->ops.elevator_merge_fn) return e->type->ops.elevator_merge_fn(q, req, bio); return ELEVATOR_NO_MERGE; } /* * Attempt to do an insertion back merge. Only check for the case where * we can append 'rq' to an existing request, so we can throw 'rq' away * afterwards. * * Returns true if we merged, false otherwise */ static bool elv_attempt_insert_merge(struct request_queue *q, struct request *rq) { struct request *__rq; if (blk_queue_nomerges(q)) return false; /* * First try one-hit cache. */ if (q->last_merge && blk_attempt_req_merge(q, q->last_merge, rq)) return true; if (blk_queue_noxmerges(q)) return false; /* * See if our hash lookup can find a potential backmerge. */ __rq = elv_rqhash_find(q, blk_rq_pos(rq)); if (__rq && blk_attempt_req_merge(q, __rq, rq)) return true; return false; } void elv_merged_request(struct request_queue *q, struct request *rq, int type) { struct elevator_queue *e = q->elevator; if (e->type->ops.elevator_merged_fn) e->type->ops.elevator_merged_fn(q, rq, type); if (type == ELEVATOR_BACK_MERGE) elv_rqhash_reposition(q, rq); q->last_merge = rq; } void elv_merge_requests(struct request_queue *q, struct request *rq, struct request *next) { struct elevator_queue *e = q->elevator; const int next_sorted = next->cmd_flags & REQ_SORTED; if (next_sorted && e->type->ops.elevator_merge_req_fn) e->type->ops.elevator_merge_req_fn(q, rq, next); elv_rqhash_reposition(q, rq); if (next_sorted) { elv_rqhash_del(q, next); q->nr_sorted--; } q->last_merge = rq; } void elv_bio_merged(struct request_queue *q, struct request *rq, struct bio *bio) { struct elevator_queue *e = q->elevator; if (e->type->ops.elevator_bio_merged_fn) e->type->ops.elevator_bio_merged_fn(q, rq, bio); } void elv_requeue_request(struct request_queue *q, struct request *rq) { /* * it already went through dequeue, we need to decrement the * in_flight count again */ if (blk_account_rq(rq)) { q->in_flight[rq_is_sync(rq)]--; if (rq->cmd_flags & REQ_SORTED) elv_deactivate_rq(q, rq); } rq->cmd_flags &= ~REQ_STARTED; __elv_add_request(q, rq, ELEVATOR_INSERT_REQUEUE); } void elv_drain_elevator(struct request_queue *q) { static int printed; lockdep_assert_held(q->queue_lock); while (q->elevator->type->ops.elevator_dispatch_fn(q, 1)) ; if (q->nr_sorted && printed++ < 10) { printk(KERN_ERR "%s: forced dispatching is broken " "(nr_sorted=%u), please report this\n", q->elevator->type->elevator_name, q->nr_sorted); } } void __elv_add_request(struct request_queue *q, struct request *rq, int where) { trace_block_rq_insert(q, rq); rq->q = q; if (rq->cmd_flags & REQ_SOFTBARRIER) { /* barriers are scheduling boundary, update end_sector */ if (rq->cmd_type == REQ_TYPE_FS || (rq->cmd_flags & REQ_DISCARD)) { q->end_sector = rq_end_sector(rq); q->boundary_rq = rq; } } else if (!(rq->cmd_flags & REQ_ELVPRIV) && (where == ELEVATOR_INSERT_SORT || where == ELEVATOR_INSERT_SORT_MERGE)) where = ELEVATOR_INSERT_BACK; switch (where) { case ELEVATOR_INSERT_REQUEUE: case ELEVATOR_INSERT_FRONT: rq->cmd_flags |= REQ_SOFTBARRIER; list_add(&rq->queuelist, &q->queue_head); break; case ELEVATOR_INSERT_BACK: rq->cmd_flags |= REQ_SOFTBARRIER; elv_drain_elevator(q); list_add_tail(&rq->queuelist, &q->queue_head); /* * We kick the queue here for the following reasons. * - The elevator might have returned NULL previously * to delay requests and returned them now. As the * queue wasn't empty before this request, ll_rw_blk * won't run the queue on return, resulting in hang. * - Usually, back inserted requests won't be merged * with anything. There's no point in delaying queue * processing. */ __blk_run_queue(q); break; case ELEVATOR_INSERT_SORT_MERGE: /* * If we succeed in merging this request with one in the * queue already, we are done - rq has now been freed, * so no need to do anything further. */ if (elv_attempt_insert_merge(q, rq)) break; case ELEVATOR_INSERT_SORT: BUG_ON(rq->cmd_type != REQ_TYPE_FS && !(rq->cmd_flags & REQ_DISCARD)); rq->cmd_flags |= REQ_SORTED; q->nr_sorted++; if (rq_mergeable(rq)) { elv_rqhash_add(q, rq); if (!q->last_merge) q->last_merge = rq; } /* * Some ioscheds (cfq) run q->request_fn directly, so * rq cannot be accessed after calling * elevator_add_req_fn. */ q->elevator->type->ops.elevator_add_req_fn(q, rq); break; case ELEVATOR_INSERT_FLUSH: rq->cmd_flags |= REQ_SOFTBARRIER; blk_insert_flush(rq); break; default: printk(KERN_ERR "%s: bad insertion point %d\n", __func__, where); BUG(); } } EXPORT_SYMBOL(__elv_add_request); void elv_add_request(struct request_queue *q, struct request *rq, int where) { unsigned long flags; spin_lock_irqsave(q->queue_lock, flags); __elv_add_request(q, rq, where); spin_unlock_irqrestore(q->queue_lock, flags); } EXPORT_SYMBOL(elv_add_request); struct request *elv_latter_request(struct request_queue *q, struct request *rq) { struct elevator_queue *e = q->elevator; if (e->type->ops.elevator_latter_req_fn) return e->type->ops.elevator_latter_req_fn(q, rq); return NULL; } struct request *elv_former_request(struct request_queue *q, struct request *rq) { struct elevator_queue *e = q->elevator; if (e->type->ops.elevator_former_req_fn) return e->type->ops.elevator_former_req_fn(q, rq); return NULL; } int elv_set_request(struct request_queue *q, struct request *rq, struct bio *bio, gfp_t gfp_mask) { struct elevator_queue *e = q->elevator; if (e->type->ops.elevator_set_req_fn) return e->type->ops.elevator_set_req_fn(q, rq, bio, gfp_mask); return 0; } void elv_put_request(struct request_queue *q, struct request *rq) { struct elevator_queue *e = q->elevator; if (e->type->ops.elevator_put_req_fn) e->type->ops.elevator_put_req_fn(rq); } int elv_may_queue(struct request_queue *q, int rw) { struct elevator_queue *e = q->elevator; if (e->type->ops.elevator_may_queue_fn) return e->type->ops.elevator_may_queue_fn(q, rw); return ELV_MQUEUE_MAY; } void elv_abort_queue(struct request_queue *q) { struct request *rq; blk_abort_flushes(q); while (!list_empty(&q->queue_head)) { rq = list_entry_rq(q->queue_head.next); rq->cmd_flags |= REQ_QUIET; trace_block_rq_abort(q, rq); /* * Mark this request as started so we don't trigger * any debug logic in the end I/O path. */ blk_start_request(rq); __blk_end_request_all(rq, -EIO); } } EXPORT_SYMBOL(elv_abort_queue); void elv_completed_request(struct request_queue *q, struct request *rq) { struct elevator_queue *e = q->elevator; /* * request is released from the driver, io must be done */ if (blk_account_rq(rq)) { q->in_flight[rq_is_sync(rq)]--; if ((rq->cmd_flags & REQ_SORTED) && e->type->ops.elevator_completed_req_fn) e->type->ops.elevator_completed_req_fn(q, rq); } } #define to_elv(atr) container_of((atr), struct elv_fs_entry, attr) static ssize_t elv_attr_show(struct kobject *kobj, struct attribute *attr, char *page) { struct elv_fs_entry *entry = to_elv(attr); struct elevator_queue *e; ssize_t error; if (!entry->show) return -EIO; e = container_of(kobj, struct elevator_queue, kobj); mutex_lock(&e->sysfs_lock); error = e->type ? entry->show(e, page) : -ENOENT; mutex_unlock(&e->sysfs_lock); return error; } static ssize_t elv_attr_store(struct kobject *kobj, struct attribute *attr, const char *page, size_t length) { struct elv_fs_entry *entry = to_elv(attr); struct elevator_queue *e; ssize_t error; if (!entry->store) return -EIO; e = container_of(kobj, struct elevator_queue, kobj); mutex_lock(&e->sysfs_lock); error = e->type ? entry->store(e, page, length) : -ENOENT; mutex_unlock(&e->sysfs_lock); return error; } static const struct sysfs_ops elv_sysfs_ops = { .show = elv_attr_show, .store = elv_attr_store, }; static struct kobj_type elv_ktype = { .sysfs_ops = &elv_sysfs_ops, .release = elevator_release, }; int elv_register_queue(struct request_queue *q) { struct elevator_queue *e = q->elevator; int error; error = kobject_add(&e->kobj, &q->kobj, "%s", "iosched"); if (!error) { struct elv_fs_entry *attr = e->type->elevator_attrs; if (attr) { while (attr->attr.name) { if (sysfs_create_file(&e->kobj, &attr->attr)) break; attr++; } } kobject_uevent(&e->kobj, KOBJ_ADD); e->registered = 1; } return error; } EXPORT_SYMBOL(elv_register_queue); void elv_unregister_queue(struct request_queue *q) { if (q) { struct elevator_queue *e = q->elevator; kobject_uevent(&e->kobj, KOBJ_REMOVE); kobject_del(&e->kobj); e->registered = 0; } } EXPORT_SYMBOL(elv_unregister_queue); int elv_register(struct elevator_type *e) { char *def = ""; /* create icq_cache if requested */ if (e->icq_size) { if (WARN_ON(e->icq_size < sizeof(struct io_cq)) || WARN_ON(e->icq_align < __alignof__(struct io_cq))) return -EINVAL; snprintf(e->icq_cache_name, sizeof(e->icq_cache_name), "%s_io_cq", e->elevator_name); e->icq_cache = kmem_cache_create(e->icq_cache_name, e->icq_size, e->icq_align, 0, NULL); if (!e->icq_cache) return -ENOMEM; } /* register, don't allow duplicate names */ spin_lock(&elv_list_lock); if (elevator_find(e->elevator_name)) { spin_unlock(&elv_list_lock); if (e->icq_cache) kmem_cache_destroy(e->icq_cache); return -EBUSY; } list_add_tail(&e->list, &elv_list); spin_unlock(&elv_list_lock); /* print pretty message */ if (!strcmp(e->elevator_name, chosen_elevator) || (!*chosen_elevator && !strcmp(e->elevator_name, CONFIG_DEFAULT_IOSCHED))) def = " (default)"; printk(KERN_INFO "io scheduler %s registered%s\n", e->elevator_name, def); return 0; } EXPORT_SYMBOL_GPL(elv_register); void elv_unregister(struct elevator_type *e) { /* unregister */ spin_lock(&elv_list_lock); list_del_init(&e->list); spin_unlock(&elv_list_lock); /* * Destroy icq_cache if it exists. icq's are RCU managed. Make * sure all RCU operations are complete before proceeding. */ if (e->icq_cache) { rcu_barrier(); kmem_cache_destroy(e->icq_cache); e->icq_cache = NULL; } } EXPORT_SYMBOL_GPL(elv_unregister); /* * switch to new_e io scheduler. be careful not to introduce deadlocks - * we don't free the old io scheduler, before we have allocated what we * need for the new one. this way we have a chance of going back to the old * one, if the new one fails init for some reason. */ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e) { struct elevator_queue *old = q->elevator; bool registered = old->registered; int err; /* * Turn on BYPASS and drain all requests w/ elevator private data. * Block layer doesn't call into a quiesced elevator - all requests * are directly put on the dispatch list without elevator data * using INSERT_BACK. All requests have SOFTBARRIER set and no * merge happens either. */ blk_queue_bypass_start(q); /* unregister and clear all auxiliary data of the old elevator */ if (registered) elv_unregister_queue(q); spin_lock_irq(q->queue_lock); ioc_clear_queue(q); spin_unlock_irq(q->queue_lock); /* allocate, init and register new elevator */ err = -ENOMEM; q->elevator = elevator_alloc(q, new_e); if (!q->elevator) goto fail_init; err = new_e->ops.elevator_init_fn(q); if (err) { kobject_put(&q->elevator->kobj); goto fail_init; } if (registered) { err = elv_register_queue(q); if (err) goto fail_register; } /* done, kill the old one and finish */ elevator_exit(old); blk_queue_bypass_end(q); blk_add_trace_msg(q, "elv switch: %s", new_e->elevator_name); return 0; fail_register: elevator_exit(q->elevator); fail_init: /* switch failed, restore and re-register old elevator */ q->elevator = old; elv_register_queue(q); blk_queue_bypass_end(q); return err; } /* * Switch this queue to the given IO scheduler. */ int elevator_change(struct request_queue *q, const char *name) { char elevator_name[ELV_NAME_MAX]; struct elevator_type *e; if (!q->elevator) return -ENXIO; strlcpy(elevator_name, name, sizeof(elevator_name)); e = elevator_get(strstrip(elevator_name)); if (!e) { printk(KERN_ERR "elevator: type %s not found\n", elevator_name); return -EINVAL; } if (!strcmp(elevator_name, q->elevator->type->elevator_name)) { elevator_put(e); return 0; } return elevator_switch(q, e); } EXPORT_SYMBOL(elevator_change); ssize_t elv_iosched_store(struct request_queue *q, const char *name, size_t count) { int ret; if (!q->elevator) return count; ret = elevator_change(q, name); if (!ret) return count; printk(KERN_ERR "elevator: switch to %s failed\n", name); return ret; } ssize_t elv_iosched_show(struct request_queue *q, char *name) { struct elevator_queue *e = q->elevator; struct elevator_type *elv; struct elevator_type *__e; int len = 0; if (!q->elevator || !blk_queue_stackable(q)) return sprintf(name, "none\n"); elv = e->type; spin_lock(&elv_list_lock); list_for_each_entry(__e, &elv_list, list) { if (!strcmp(elv->elevator_name, __e->elevator_name)) len += sprintf(name+len, "[%s] ", elv->elevator_name); else len += sprintf(name+len, "%s ", __e->elevator_name); } spin_unlock(&elv_list_lock); len += sprintf(len+name, "\n"); return len; } struct request *elv_rb_former_request(struct request_queue *q, struct request *rq) { struct rb_node *rbprev = rb_prev(&rq->rb_node); if (rbprev) return rb_entry_rq(rbprev); return NULL; } EXPORT_SYMBOL(elv_rb_former_request); struct request *elv_rb_latter_request(struct request_queue *q, struct request *rq) { struct rb_node *rbnext = rb_next(&rq->rb_node); if (rbnext) return rb_entry_rq(rbnext); return NULL; } EXPORT_SYMBOL(elv_rb_latter_request);