diff options
Diffstat (limited to 'block/elevator.c')
| -rw-r--r-- | block/elevator.c | 1198 |
1 files changed, 1198 insertions, 0 deletions
diff --git a/block/elevator.c b/block/elevator.c new file mode 100644 index 000000000..72ce7a4a2 --- /dev/null +++ b/block/elevator.c @@ -0,0 +1,1198 @@ +/* + * 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 <linux/pm_runtime.h> +#include <linux/blk-cgroup.h> + +#include <trace/events/block.h> + +#include "blk.h" +#include "blk-mq-sched.h" +#include "blk-wbt.h" + +static DEFINE_SPINLOCK(elv_list_lock); +static LIST_HEAD(elv_list); + +/* + * Merge hash stuff. + */ +#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_bio_merge(struct request *rq, struct bio *bio) +{ + struct request_queue *q = rq->q; + struct elevator_queue *e = q->elevator; + + if (e->uses_mq && e->type->ops.mq.allow_merge) + return e->type->ops.mq.allow_merge(q, rq, bio); + else if (!e->uses_mq && e->type->ops.sq.elevator_allow_bio_merge_fn) + return e->type->ops.sq.elevator_allow_bio_merge_fn(q, rq, bio); + + return 1; +} + +/* + * can we safely merge with this request? + */ +bool elv_bio_merge_ok(struct request *rq, struct bio *bio) +{ + if (!blk_rq_merge_ok(rq, bio)) + return false; + + if (!elv_iosched_allow_bio_merge(rq, bio)) + return false; + + return true; +} +EXPORT_SYMBOL(elv_bio_merge_ok); + +static bool elevator_match(const struct elevator_type *e, const char *name) +{ + if (!strcmp(e->elevator_name, name)) + return true; + if (e->elevator_alias && !strcmp(e->elevator_alias, name)) + return true; + + return false; +} + +/* + * Return scheduler with name 'name' and with matching 'mq capability + */ +static struct elevator_type *elevator_find(const char *name, bool mq) +{ + struct elevator_type *e; + + list_for_each_entry(e, &elv_list, list) { + if (elevator_match(e, name) && (mq == e->uses_mq)) + return e; + } + + return NULL; +} + +static void elevator_put(struct elevator_type *e) +{ + module_put(e->elevator_owner); +} + +static struct elevator_type *elevator_get(struct request_queue *q, + const char *name, bool try_loading) +{ + struct elevator_type *e; + + spin_lock(&elv_list_lock); + + e = elevator_find(name, q->mq_ops != NULL); + if (!e && try_loading) { + spin_unlock(&elv_list_lock); + request_module("%s-iosched", name); + spin_lock(&elv_list_lock); + e = elevator_find(name, q->mq_ops != NULL); + } + + 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); + +/* called during boot to load the elevator chosen by the elevator param */ +void __init load_default_elevator_module(void) +{ + struct elevator_type *e; + + if (!chosen_elevator[0]) + return; + + /* + * Boot parameter is deprecated, we haven't supported that for MQ. + * Only look for non-mq schedulers from here. + */ + spin_lock(&elv_list_lock); + e = elevator_find(chosen_elevator, false); + spin_unlock(&elv_list_lock); + + if (!e) + request_module("%s-iosched", chosen_elevator); +} + +static struct kobj_type elv_ktype; + +struct elevator_queue *elevator_alloc(struct request_queue *q, + struct elevator_type *e) +{ + struct elevator_queue *eq; + + eq = kzalloc_node(sizeof(*eq), GFP_KERNEL, q->node); + if (unlikely(!eq)) + return NULL; + + eq->type = e; + kobject_init(&eq->kobj, &elv_ktype); + mutex_init(&eq->sysfs_lock); + hash_init(eq->hash); + eq->uses_mq = e->uses_mq; + + return eq; +} +EXPORT_SYMBOL(elevator_alloc); + +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); +} + +/* + * Use the default elevator specified by config boot param for non-mq devices, + * or by config option. Don't try to load modules as we could be running off + * async and request_module() isn't allowed from async. + */ +int elevator_init(struct request_queue *q) +{ + struct elevator_type *e = NULL; + int err = 0; + + /* + * q->sysfs_lock must be held to provide mutual exclusion between + * elevator_switch() and here. + */ + mutex_lock(&q->sysfs_lock); + if (unlikely(q->elevator)) + goto out_unlock; + + if (*chosen_elevator) { + e = elevator_get(q, chosen_elevator, false); + if (!e) + printk(KERN_ERR "I/O scheduler %s not found\n", + chosen_elevator); + } + + if (!e) + e = elevator_get(q, CONFIG_DEFAULT_IOSCHED, false); + if (!e) { + printk(KERN_ERR + "Default I/O scheduler not found. Using noop.\n"); + e = elevator_get(q, "noop", false); + } + + err = e->ops.sq.elevator_init_fn(q, e); + if (err) + elevator_put(e); +out_unlock: + mutex_unlock(&q->sysfs_lock); + return err; +} + +void elevator_exit(struct request_queue *q, struct elevator_queue *e) +{ + mutex_lock(&e->sysfs_lock); + if (e->uses_mq && e->type->ops.mq.exit_sched) + blk_mq_exit_sched(q, e); + else if (!e->uses_mq && e->type->ops.sq.elevator_exit_fn) + e->type->ops.sq.elevator_exit_fn(e); + mutex_unlock(&e->sysfs_lock); + + kobject_put(&e->kobj); +} + +static inline void __elv_rqhash_del(struct request *rq) +{ + hash_del(&rq->hash); + rq->rq_flags &= ~RQF_HASHED; +} + +void elv_rqhash_del(struct request_queue *q, struct request *rq) +{ + if (ELV_ON_HASH(rq)) + __elv_rqhash_del(rq); +} +EXPORT_SYMBOL_GPL(elv_rqhash_del); + +void elv_rqhash_add(struct request_queue *q, struct request *rq) +{ + struct elevator_queue *e = q->elevator; + + BUG_ON(ELV_ON_HASH(rq)); + hash_add(e->hash, &rq->hash, rq_hash_key(rq)); + rq->rq_flags |= RQF_HASHED; +} +EXPORT_SYMBOL_GPL(elv_rqhash_add); + +void elv_rqhash_reposition(struct request_queue *q, struct request *rq) +{ + __elv_rqhash_del(rq); + elv_rqhash_add(q, rq); +} + +struct request *elv_rqhash_find(struct request_queue *q, sector_t offset) +{ + struct elevator_queue *e = q->elevator; + struct hlist_node *next; + struct request *rq; + + hash_for_each_possible_safe(e->hash, rq, next, hash, offset) { + 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; + + if (q->last_merge == rq) + q->last_merge = NULL; + + elv_rqhash_del(q, rq); + + q->nr_sorted--; + + boundary = q->end_sector; + list_for_each_prev(entry, &q->queue_head) { + struct request *pos = list_entry_rq(entry); + + if (req_op(rq) != req_op(pos)) + break; + if (rq_data_dir(rq) != rq_data_dir(pos)) + break; + if (pos->rq_flags & (RQF_STARTED | RQF_SOFTBARRIER)) + 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); + +enum elv_merge elv_merge(struct request_queue *q, struct request **req, + struct bio *bio) +{ + struct elevator_queue *e = q->elevator; + struct request *__rq; + + /* + * 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) || !bio_mergeable(bio)) + return ELEVATOR_NO_MERGE; + + /* + * First try one-hit cache. + */ + if (q->last_merge && elv_bio_merge_ok(q->last_merge, bio)) { + enum elv_merge 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_iter.bi_sector); + if (__rq && elv_bio_merge_ok(__rq, bio)) { + *req = __rq; + return ELEVATOR_BACK_MERGE; + } + + if (e->uses_mq && e->type->ops.mq.request_merge) + return e->type->ops.mq.request_merge(q, req, bio); + else if (!e->uses_mq && e->type->ops.sq.elevator_merge_fn) + return e->type->ops.sq.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 + */ +bool elv_attempt_insert_merge(struct request_queue *q, struct request *rq) +{ + struct request *__rq; + bool ret; + + 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; + + ret = false; + /* + * See if our hash lookup can find a potential backmerge. + */ + while (1) { + __rq = elv_rqhash_find(q, blk_rq_pos(rq)); + if (!__rq || !blk_attempt_req_merge(q, __rq, rq)) + break; + + /* The merged request could be merged with others, try again */ + ret = true; + rq = __rq; + } + + return ret; +} + +void elv_merged_request(struct request_queue *q, struct request *rq, + enum elv_merge type) +{ + struct elevator_queue *e = q->elevator; + + if (e->uses_mq && e->type->ops.mq.request_merged) + e->type->ops.mq.request_merged(q, rq, type); + else if (!e->uses_mq && e->type->ops.sq.elevator_merged_fn) + e->type->ops.sq.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; + bool next_sorted = false; + + if (e->uses_mq && e->type->ops.mq.requests_merged) + e->type->ops.mq.requests_merged(q, rq, next); + else if (e->type->ops.sq.elevator_merge_req_fn) { + next_sorted = (__force bool)(next->rq_flags & RQF_SORTED); + if (next_sorted) + e->type->ops.sq.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 (WARN_ON_ONCE(e->uses_mq)) + return; + + if (e->type->ops.sq.elevator_bio_merged_fn) + e->type->ops.sq.elevator_bio_merged_fn(q, rq, bio); +} + +#ifdef CONFIG_PM +static void blk_pm_requeue_request(struct request *rq) +{ + if (rq->q->dev && !(rq->rq_flags & RQF_PM)) + rq->q->nr_pending--; +} + +static void blk_pm_add_request(struct request_queue *q, struct request *rq) +{ + if (q->dev && !(rq->rq_flags & RQF_PM) && q->nr_pending++ == 0 && + (q->rpm_status == RPM_SUSPENDED || q->rpm_status == RPM_SUSPENDING)) + pm_request_resume(q->dev); +} +#else +static inline void blk_pm_requeue_request(struct request *rq) {} +static inline void blk_pm_add_request(struct request_queue *q, + struct request *rq) +{ +} +#endif + +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->rq_flags & RQF_SORTED) + elv_deactivate_rq(q, rq); + } + + rq->rq_flags &= ~RQF_STARTED; + + blk_pm_requeue_request(rq); + + __elv_add_request(q, rq, ELEVATOR_INSERT_REQUEUE); +} + +void elv_drain_elevator(struct request_queue *q) +{ + struct elevator_queue *e = q->elevator; + static int printed; + + if (WARN_ON_ONCE(e->uses_mq)) + return; + + lockdep_assert_held(q->queue_lock); + + while (e->type->ops.sq.elevator_dispatch_fn(q, 1)) + ; + if (q->nr_sorted && !blk_queue_is_zoned(q) && 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); + + blk_pm_add_request(q, rq); + + rq->q = q; + + if (rq->rq_flags & RQF_SOFTBARRIER) { + /* barriers are scheduling boundary, update end_sector */ + if (!blk_rq_is_passthrough(rq)) { + q->end_sector = rq_end_sector(rq); + q->boundary_rq = rq; + } + } else if (!(rq->rq_flags & RQF_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->rq_flags |= RQF_SOFTBARRIER; + list_add(&rq->queuelist, &q->queue_head); + break; + + case ELEVATOR_INSERT_BACK: + rq->rq_flags |= RQF_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; + /* fall through */ + case ELEVATOR_INSERT_SORT: + BUG_ON(blk_rq_is_passthrough(rq)); + rq->rq_flags |= RQF_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.sq.elevator_add_req_fn(q, rq); + break; + + case ELEVATOR_INSERT_FLUSH: + rq->rq_flags |= RQF_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->uses_mq && e->type->ops.mq.next_request) + return e->type->ops.mq.next_request(q, rq); + else if (!e->uses_mq && e->type->ops.sq.elevator_latter_req_fn) + return e->type->ops.sq.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->uses_mq && e->type->ops.mq.former_request) + return e->type->ops.mq.former_request(q, rq); + if (!e->uses_mq && e->type->ops.sq.elevator_former_req_fn) + return e->type->ops.sq.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 (WARN_ON_ONCE(e->uses_mq)) + return 0; + + if (e->type->ops.sq.elevator_set_req_fn) + return e->type->ops.sq.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 (WARN_ON_ONCE(e->uses_mq)) + return; + + if (e->type->ops.sq.elevator_put_req_fn) + e->type->ops.sq.elevator_put_req_fn(rq); +} + +int elv_may_queue(struct request_queue *q, unsigned int op) +{ + struct elevator_queue *e = q->elevator; + + if (WARN_ON_ONCE(e->uses_mq)) + return 0; + + if (e->type->ops.sq.elevator_may_queue_fn) + return e->type->ops.sq.elevator_may_queue_fn(q, op); + + return ELV_MQUEUE_MAY; +} + +void elv_completed_request(struct request_queue *q, struct request *rq) +{ + struct elevator_queue *e = q->elevator; + + if (WARN_ON_ONCE(e->uses_mq)) + return; + + /* + * request is released from the driver, io must be done + */ + if (blk_account_rq(rq)) { + q->in_flight[rq_is_sync(rq)]--; + if ((rq->rq_flags & RQF_SORTED) && + e->type->ops.sq.elevator_completed_req_fn) + e->type->ops.sq.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, +}; + +/* + * elv_register_queue is called from either blk_register_queue or + * elevator_switch, elevator switch is prevented from being happen + * in the two paths, so it is safe to not hold q->sysfs_lock. + */ +int elv_register_queue(struct request_queue *q, bool uevent) +{ + 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++; + } + } + if (uevent) + kobject_uevent(&e->kobj, KOBJ_ADD); + + e->registered = 1; + if (!e->uses_mq && e->type->ops.sq.elevator_registered_fn) + e->type->ops.sq.elevator_registered_fn(q); + } + return error; +} + +/* + * elv_unregister_queue is called from either blk_unregister_queue or + * elevator_switch, elevator switch is prevented from being happen + * in the two paths, so it is safe to not hold q->sysfs_lock. + */ +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; + } +} + +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, e->uses_mq)) { + spin_unlock(&elv_list_lock); + kmem_cache_destroy(e->icq_cache); + return -EBUSY; + } + list_add_tail(&e->list, &elv_list); + spin_unlock(&elv_list_lock); + + /* print pretty message */ + if (elevator_match(e, chosen_elevator) || + (!*chosen_elevator && + elevator_match(e, 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); + +int elevator_switch_mq(struct request_queue *q, + struct elevator_type *new_e) +{ + int ret; + + lockdep_assert_held(&q->sysfs_lock); + + if (q->elevator) { + if (q->elevator->registered) + elv_unregister_queue(q); + + ioc_clear_queue(q); + elevator_exit(q, q->elevator); + } + + ret = blk_mq_init_sched(q, new_e); + if (ret) + goto out; + + if (new_e) { + ret = elv_register_queue(q, true); + if (ret) { + elevator_exit(q, q->elevator); + goto out; + } + } + + if (new_e) + blk_add_trace_msg(q, "elv switch: %s", new_e->elevator_name); + else + blk_add_trace_msg(q, "elv switch: none"); + +out: + return ret; +} + +/* + * For blk-mq devices, we default to using mq-deadline, if available, for single + * queue devices. If deadline isn't available OR we have multiple queues, + * default to "none". + */ +int elevator_init_mq(struct request_queue *q) +{ + struct elevator_type *e; + int err = 0; + + if (q->nr_hw_queues != 1) + return 0; + + WARN_ON_ONCE(test_bit(QUEUE_FLAG_REGISTERED, &q->queue_flags)); + + if (unlikely(q->elevator)) + goto out; + + e = elevator_get(q, "mq-deadline", false); + if (!e) + goto out; + + err = blk_mq_init_sched(q, e); + if (err) + elevator_put(e); +out: + return err; +} + + +/* + * 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 old_registered = false; + int err; + + lockdep_assert_held(&q->sysfs_lock); + + if (q->mq_ops) { + blk_mq_freeze_queue(q); + blk_mq_quiesce_queue(q); + + err = elevator_switch_mq(q, new_e); + + blk_mq_unquiesce_queue(q); + blk_mq_unfreeze_queue(q); + + return 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. + */ + if (old) { + old_registered = old->registered; + + blk_queue_bypass_start(q); + + /* unregister and clear all auxiliary data of the old elevator */ + if (old_registered) + elv_unregister_queue(q); + + ioc_clear_queue(q); + } + + /* allocate, init and register new elevator */ + err = new_e->ops.sq.elevator_init_fn(q, new_e); + if (err) + goto fail_init; + + err = elv_register_queue(q, true); + if (err) + goto fail_register; + + /* done, kill the old one and finish */ + if (old) { + elevator_exit(q, 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, q->elevator); +fail_init: + /* switch failed, restore and re-register old elevator */ + if (old) { + q->elevator = old; + elv_register_queue(q, true); + blk_queue_bypass_end(q); + } + + return err; +} + +/* + * Switch this queue to the given IO scheduler. + */ +static int __elevator_change(struct request_queue *q, const char *name) +{ + char elevator_name[ELV_NAME_MAX]; + struct elevator_type *e; + + /* Make sure queue is not in the middle of being removed */ + if (!blk_queue_registered(q)) + return -ENOENT; + + /* + * Special case for mq, turn off scheduling + */ + if (q->mq_ops && !strncmp(name, "none", 4)) + return elevator_switch(q, NULL); + + strlcpy(elevator_name, name, sizeof(elevator_name)); + e = elevator_get(q, strstrip(elevator_name), true); + if (!e) + return -EINVAL; + + if (q->elevator && elevator_match(q->elevator->type, elevator_name)) { + elevator_put(e); + return 0; + } + + return elevator_switch(q, e); +} + +static inline bool elv_support_iosched(struct request_queue *q) +{ + if (q->mq_ops && q->tag_set && (q->tag_set->flags & + BLK_MQ_F_NO_SCHED)) + return false; + return true; +} + +ssize_t elv_iosched_store(struct request_queue *q, const char *name, + size_t count) +{ + int ret; + + if (!(q->mq_ops || q->request_fn) || !elv_support_iosched(q)) + return count; + + ret = __elevator_change(q, name); + if (!ret) + return count; + + return ret; +} + +ssize_t elv_iosched_show(struct request_queue *q, char *name) +{ + struct elevator_queue *e = q->elevator; + struct elevator_type *elv = NULL; + struct elevator_type *__e; + bool uses_mq = q->mq_ops != NULL; + int len = 0; + + if (!queue_is_rq_based(q)) + return sprintf(name, "none\n"); + + if (!q->elevator) + len += sprintf(name+len, "[none] "); + else + elv = e->type; + + spin_lock(&elv_list_lock); + list_for_each_entry(__e, &elv_list, list) { + if (elv && elevator_match(elv, __e->elevator_name) && + (__e->uses_mq == uses_mq)) { + len += sprintf(name+len, "[%s] ", elv->elevator_name); + continue; + } + if (__e->uses_mq && q->mq_ops && elv_support_iosched(q)) + len += sprintf(name+len, "%s ", __e->elevator_name); + else if (!__e->uses_mq && !q->mq_ops) + len += sprintf(name+len, "%s ", __e->elevator_name); + } + spin_unlock(&elv_list_lock); + + if (q->mq_ops && q->elevator) + len += sprintf(name+len, "none"); + + 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); |