diff options
Diffstat (limited to 'block/elevator.c')
| -rw-r--r-- | block/elevator.c | 1119 |
1 files changed, 1119 insertions, 0 deletions
diff --git a/block/elevator.c b/block/elevator.c new file mode 100644 index 00000000..b0b38ce0 --- /dev/null +++ b/block/elevator.c @@ -0,0 +1,1119 @@ +/* + * 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/delay.h> +#include <linux/blktrace_api.h> +#include <linux/hash.h> +#include <linux/uaccess.h> + +#include <trace/events/block.h> + +#include "blk.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->ops->elevator_allow_merge_fn) + return e->ops->elevator_allow_merge_fn(q, rq, bio); + + return 1; +} + +/* + * can we safely merge with this request? + */ +int elv_rq_merge_ok(struct request *rq, struct bio *bio) +{ + if (!rq_mergeable(rq)) + return 0; + + /* + * Don't merge file system requests and discard requests + */ + if ((bio->bi_rw & REQ_DISCARD) != (rq->bio->bi_rw & REQ_DISCARD)) + return 0; + + /* + * Don't merge discard requests and secure discard requests + */ + if ((bio->bi_rw & REQ_SECURE) != (rq->bio->bi_rw & REQ_SECURE)) + return 0; + + /* + * different data direction or already started, don't merge + */ + if (bio_data_dir(bio) != rq_data_dir(rq)) + return 0; + + /* + * must be same device and not a special request + */ + if (rq->rq_disk != bio->bi_bdev->bd_disk || rq->special) + return 0; + + /* + * only merge integrity protected bio into ditto rq + */ + if (bio_integrity(bio) != blk_integrity_rq(rq)) + return 0; + + if (!elv_iosched_allow_merge(rq, bio)) + return 0; + + return 1; +} +EXPORT_SYMBOL(elv_rq_merge_ok); + +int elv_try_merge(struct request *__rq, struct bio *bio) +{ + int ret = ELEVATOR_NO_MERGE; + + /* + * we can merge and sequence is ok, check if it's possible + */ + if (elv_rq_merge_ok(__rq, bio)) { + if (blk_rq_pos(__rq) + blk_rq_sectors(__rq) == bio->bi_sector) + ret = ELEVATOR_BACK_MERGE; + else if (blk_rq_pos(__rq) - bio_sectors(bio) == bio->bi_sector) + ret = ELEVATOR_FRONT_MERGE; + } + + return ret; +} + +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 void *elevator_init_queue(struct request_queue *q, + struct elevator_queue *eq) +{ + return eq->ops->elevator_init_fn(q); +} + +static void elevator_attach(struct request_queue *q, struct elevator_queue *eq, + void *data) +{ + q->elevator = eq; + eq->elevator_data = data; +} + +static char chosen_elevator[16]; + +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->ops = &e->ops; + eq->elevator_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->elevator_type); + kfree(e->hash); + kfree(e); +} + +int elevator_init(struct request_queue *q, char *name) +{ + struct elevator_type *e = NULL; + struct elevator_queue *eq; + void *data; + + 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"); + } + } + + eq = elevator_alloc(q, e); + if (!eq) + return -ENOMEM; + + data = elevator_init_queue(q, eq); + if (!data) { + kobject_put(&eq->kobj); + return -ENOMEM; + } + + elevator_attach(q, eq, data); + return 0; +} +EXPORT_SYMBOL(elevator_init); + +void elevator_exit(struct elevator_queue *e) +{ + mutex_lock(&e->sysfs_lock); + if (e->ops->elevator_exit_fn) + e->ops->elevator_exit_fn(e); + e->ops = NULL; + 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. + */ +struct request *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; + else + return __rq; + } + + rb_link_node(&rq->rb_node, parent, p); + rb_insert_color(&rq->rb_node, root); + return NULL; +} +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) { + ret = elv_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->ops->elevator_merge_fn) + return e->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->ops->elevator_merged_fn) + e->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->ops->elevator_merge_req_fn) + e->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->ops->elevator_bio_merged_fn) + e->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; + while (q->elevator->ops->elevator_dispatch_fn(q, 1)) + ; + if (q->nr_sorted == 0) + return; + if (printed++ < 10) { + printk(KERN_ERR "%s: forced dispatching is broken " + "(nr_sorted=%u), please report this\n", + q->elevator->elevator_type->elevator_name, q->nr_sorted); + } +} + +/* + * Call with queue lock held, interrupts disabled + */ +void elv_quiesce_start(struct request_queue *q) +{ + if (!q->elevator) + return; + + queue_flag_set(QUEUE_FLAG_ELVSWITCH, q); + + /* + * make sure we don't have any requests in flight + */ + elv_drain_elevator(q); + while (q->rq.elvpriv) { + __blk_run_queue(q); + spin_unlock_irq(q->queue_lock); + msleep(10); + spin_lock_irq(q->queue_lock); + elv_drain_elevator(q); + } +} + +void elv_quiesce_end(struct request_queue *q) +{ + queue_flag_clear(QUEUE_FLAG_ELVSWITCH, q); +} + +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->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->ops->elevator_latter_req_fn) + return e->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->ops->elevator_former_req_fn) + return e->ops->elevator_former_req_fn(q, rq); + return NULL; +} + +int elv_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask) +{ + struct elevator_queue *e = q->elevator; + + if (e->ops->elevator_set_req_fn) + return e->ops->elevator_set_req_fn(q, rq, gfp_mask); + + rq->elevator_private[0] = NULL; + return 0; +} + +void elv_put_request(struct request_queue *q, struct request *rq) +{ + struct elevator_queue *e = q->elevator; + + if (e->ops->elevator_put_req_fn) + e->ops->elevator_put_req_fn(rq); +} + +int elv_may_queue(struct request_queue *q, int rw) +{ + struct elevator_queue *e = q->elevator; + + if (e->ops->elevator_may_queue_fn) + return e->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->ops->elevator_completed_req_fn) + e->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->ops ? 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->ops ? 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->elevator_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); + +static void __elv_unregister_queue(struct elevator_queue *e) +{ + kobject_uevent(&e->kobj, KOBJ_REMOVE); + kobject_del(&e->kobj); + e->registered = 0; +} + +void elv_unregister_queue(struct request_queue *q) +{ + if (q) + __elv_unregister_queue(q->elevator); +} +EXPORT_SYMBOL(elv_unregister_queue); + +void elv_register(struct elevator_type *e) +{ + char *def = ""; + + spin_lock(&elv_list_lock); + BUG_ON(elevator_find(e->elevator_name)); + list_add_tail(&e->list, &elv_list); + spin_unlock(&elv_list_lock); + + 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); +} +EXPORT_SYMBOL_GPL(elv_register); + +void elv_unregister(struct elevator_type *e) +{ + struct task_struct *g, *p; + + /* + * Iterate every thread in the process to remove the io contexts. + */ + if (e->ops.trim) { + read_lock(&tasklist_lock); + do_each_thread(g, p) { + task_lock(p); + if (p->io_context) + e->ops.trim(p->io_context); + task_unlock(p); + } while_each_thread(g, p); + read_unlock(&tasklist_lock); + } + + spin_lock(&elv_list_lock); + list_del_init(&e->list); + spin_unlock(&elv_list_lock); +} +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_elevator, *e; + void *data; + int err; + + /* + * Allocate new elevator + */ + e = elevator_alloc(q, new_e); + if (!e) + return -ENOMEM; + + data = elevator_init_queue(q, e); + if (!data) { + kobject_put(&e->kobj); + return -ENOMEM; + } + + /* + * Turn on BYPASS and drain all requests w/ elevator private data + */ + spin_lock_irq(q->queue_lock); + elv_quiesce_start(q); + + /* + * Remember old elevator. + */ + old_elevator = q->elevator; + + /* + * attach and start new elevator + */ + elevator_attach(q, e, data); + + spin_unlock_irq(q->queue_lock); + + if (old_elevator->registered) { + __elv_unregister_queue(old_elevator); + + err = elv_register_queue(q); + if (err) + goto fail_register; + } + + /* + * finally exit old elevator and turn off BYPASS. + */ + elevator_exit(old_elevator); + spin_lock_irq(q->queue_lock); + elv_quiesce_end(q); + spin_unlock_irq(q->queue_lock); + + blk_add_trace_msg(q, "elv switch: %s", e->elevator_type->elevator_name); + + return 0; + +fail_register: + /* + * switch failed, exit the new io scheduler and reattach the old + * one again (along with re-adding the sysfs dir) + */ + elevator_exit(e); + q->elevator = old_elevator; + elv_register_queue(q); + + spin_lock_irq(q->queue_lock); + queue_flag_clear(QUEUE_FLAG_ELVSWITCH, q); + spin_unlock_irq(q->queue_lock); + + 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->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->elevator_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); |