diff options
Diffstat (limited to 'block/elevator.c')
| -rw-r--r-- | block/elevator.c | 824 |
1 files changed, 824 insertions, 0 deletions
diff --git a/block/elevator.c b/block/elevator.c new file mode 100644 index 000000000..5ff093cb3 --- /dev/null +++ b/block/elevator.c @@ -0,0 +1,824 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * 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/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 <trace/events/block.h> + +#include "elevator.h" +#include "blk.h" +#include "blk-mq-sched.h" +#include "blk-pm.h" +#include "blk-wbt.h" +#include "blk-cgroup.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 bool 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->type->ops.allow_merge) + return e->type->ops.allow_merge(q, rq, bio); + + return true; +} + +/* + * 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 inline bool elv_support_features(struct request_queue *q, + const struct elevator_type *e) +{ + return (q->required_elevator_features & e->elevator_features) == + q->required_elevator_features; +} + +/** + * elevator_match - Check whether @e's name or alias matches @name + * @e: Scheduler to test + * @name: Elevator name to test + * + * Return true if the elevator @e's name or alias matches @name. + */ +static bool elevator_match(const struct elevator_type *e, const char *name) +{ + return !strcmp(e->elevator_name, name) || + (e->elevator_alias && !strcmp(e->elevator_alias, name)); +} + +static struct elevator_type *__elevator_find(const char *name) +{ + struct elevator_type *e; + + list_for_each_entry(e, &elv_list, list) + if (elevator_match(e, name)) + return e; + return NULL; +} + +static struct elevator_type *elevator_find_get(struct request_queue *q, + const char *name) +{ + struct elevator_type *e; + + spin_lock(&elv_list_lock); + e = __elevator_find(name); + if (e && (!elv_support_features(q, e) || !elevator_tryget(e))) + e = NULL; + spin_unlock(&elv_list_lock); + return e; +} + +static const 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; + + __elevator_get(e); + eq->type = e; + kobject_init(&eq->kobj, &elv_ktype); + mutex_init(&eq->sysfs_lock); + hash_init(eq->hash); + + 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); +} + +void elevator_exit(struct request_queue *q) +{ + struct elevator_queue *e = q->elevator; + + ioc_clear_queue(q); + blk_mq_sched_free_rqs(q); + + mutex_lock(&e->sysfs_lock); + blk_mq_exit_sched(q, 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); + +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; + + if (blk_discard_mergable(__rq)) + return ELEVATOR_DISCARD_MERGE; + return ELEVATOR_BACK_MERGE; + } + + if (e->type->ops.request_merge) + return e->type->ops.request_merge(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. 'free' will contain all + * requests that need to be freed. + */ +bool elv_attempt_insert_merge(struct request_queue *q, struct request *rq, + struct list_head *free) +{ + 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)) { + list_add(&rq->queuelist, free); + 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; + + list_add(&rq->queuelist, free); + /* 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->type->ops.request_merged) + e->type->ops.request_merged(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; + + if (e->type->ops.requests_merged) + e->type->ops.requests_merged(q, rq, next); + + elv_rqhash_reposition(q, rq); + q->last_merge = rq; +} + +struct request *elv_latter_request(struct request_queue *q, struct request *rq) +{ + struct elevator_queue *e = q->elevator; + + if (e->type->ops.next_request) + return e->type->ops.next_request(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.former_request) + return e->type->ops.former_request(q, rq); + + return NULL; +} + +#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 const struct kobj_type elv_ktype = { + .sysfs_ops = &elv_sysfs_ops, + .release = elevator_release, +}; + +int elv_register_queue(struct request_queue *q, bool uevent) +{ + struct elevator_queue *e = q->elevator; + int error; + + lockdep_assert_held(&q->sysfs_lock); + + error = kobject_add(&e->kobj, &q->disk->queue_kobj, "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); + + set_bit(ELEVATOR_FLAG_REGISTERED, &e->flags); + } + return error; +} + +void elv_unregister_queue(struct request_queue *q) +{ + struct elevator_queue *e = q->elevator; + + lockdep_assert_held(&q->sysfs_lock); + + if (e && test_and_clear_bit(ELEVATOR_FLAG_REGISTERED, &e->flags)) { + kobject_uevent(&e->kobj, KOBJ_REMOVE); + kobject_del(&e->kobj); + } +} + +int elv_register(struct elevator_type *e) +{ + /* finish request is mandatory */ + if (WARN_ON_ONCE(!e->ops.finish_request)) + return -EINVAL; + /* insert_requests and dispatch_request are mandatory */ + if (WARN_ON_ONCE(!e->ops.insert_requests || !e->ops.dispatch_request)) + return -EINVAL; + + /* 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); + kmem_cache_destroy(e->icq_cache); + return -EBUSY; + } + list_add_tail(&e->list, &elv_list); + spin_unlock(&elv_list_lock); + + printk(KERN_INFO "io scheduler %s registered\n", e->elevator_name); + + 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); + +static inline bool elv_support_iosched(struct request_queue *q) +{ + if (!queue_is_mq(q) || + (q->tag_set && (q->tag_set->flags & BLK_MQ_F_NO_SCHED))) + return false; + return true; +} + +/* + * For single queue devices, default to using mq-deadline. If we have multiple + * queues or mq-deadline is not available, default to "none". + */ +static struct elevator_type *elevator_get_default(struct request_queue *q) +{ + if (q->tag_set && q->tag_set->flags & BLK_MQ_F_NO_SCHED_BY_DEFAULT) + return NULL; + + if (q->nr_hw_queues != 1 && + !blk_mq_is_shared_tags(q->tag_set->flags)) + return NULL; + + return elevator_find_get(q, "mq-deadline"); +} + +/* + * Get the first elevator providing the features required by the request queue. + * Default to "none" if no matching elevator is found. + */ +static struct elevator_type *elevator_get_by_features(struct request_queue *q) +{ + struct elevator_type *e, *found = NULL; + + spin_lock(&elv_list_lock); + + list_for_each_entry(e, &elv_list, list) { + if (elv_support_features(q, e)) { + found = e; + break; + } + } + + if (found && !elevator_tryget(found)) + found = NULL; + + spin_unlock(&elv_list_lock); + return found; +} + +/* + * For a device queue that has no required features, use the default elevator + * settings. Otherwise, use the first elevator available matching the required + * features. If no suitable elevator is find or if the chosen elevator + * initialization fails, fall back to the "none" elevator (no elevator). + */ +void elevator_init_mq(struct request_queue *q) +{ + struct elevator_type *e; + int err; + + if (!elv_support_iosched(q)) + return; + + WARN_ON_ONCE(blk_queue_registered(q)); + + if (unlikely(q->elevator)) + return; + + if (!q->required_elevator_features) + e = elevator_get_default(q); + else + e = elevator_get_by_features(q); + if (!e) + return; + + /* + * We are called before adding disk, when there isn't any FS I/O, + * so freezing queue plus canceling dispatch work is enough to + * drain any dispatch activities originated from passthrough + * requests, then no need to quiesce queue which may add long boot + * latency, especially when lots of disks are involved. + */ + blk_mq_freeze_queue(q); + blk_mq_cancel_work_sync(q); + + err = blk_mq_init_sched(q, e); + + blk_mq_unfreeze_queue(q); + + if (err) { + pr_warn("\"%s\" elevator initialization failed, " + "falling back to \"none\"\n", e->elevator_name); + } + + elevator_put(e); +} + +/* + * Switch to new_e io scheduler. + * + * If switching fails, we are most likely running out of memory and not able + * to restore the old io scheduler, so leaving the io scheduler being none. + */ +int elevator_switch(struct request_queue *q, struct elevator_type *new_e) +{ + int ret; + + lockdep_assert_held(&q->sysfs_lock); + + blk_mq_freeze_queue(q); + blk_mq_quiesce_queue(q); + + if (q->elevator) { + elv_unregister_queue(q); + elevator_exit(q); + } + + ret = blk_mq_init_sched(q, new_e); + if (ret) + goto out_unfreeze; + + ret = elv_register_queue(q, true); + if (ret) { + elevator_exit(q); + goto out_unfreeze; + } + blk_add_trace_msg(q, "elv switch: %s", new_e->elevator_name); + +out_unfreeze: + blk_mq_unquiesce_queue(q); + blk_mq_unfreeze_queue(q); + + if (ret) { + pr_warn("elv: switch to \"%s\" failed, falling back to \"none\"\n", + new_e->elevator_name); + } + + return ret; +} + +void elevator_disable(struct request_queue *q) +{ + lockdep_assert_held(&q->sysfs_lock); + + blk_mq_freeze_queue(q); + blk_mq_quiesce_queue(q); + + elv_unregister_queue(q); + elevator_exit(q); + blk_queue_flag_clear(QUEUE_FLAG_SQ_SCHED, q); + q->elevator = NULL; + q->nr_requests = q->tag_set->queue_depth; + blk_add_trace_msg(q, "elv switch: none"); + + blk_mq_unquiesce_queue(q); + blk_mq_unfreeze_queue(q); +} + +/* + * Switch this queue to the given IO scheduler. + */ +static int elevator_change(struct request_queue *q, const char *elevator_name) +{ + struct elevator_type *e; + int ret; + + /* Make sure queue is not in the middle of being removed */ + if (!blk_queue_registered(q)) + return -ENOENT; + + if (!strncmp(elevator_name, "none", 4)) { + if (q->elevator) + elevator_disable(q); + return 0; + } + + if (q->elevator && elevator_match(q->elevator->type, elevator_name)) + return 0; + + e = elevator_find_get(q, elevator_name); + if (!e) { + request_module("%s-iosched", elevator_name); + e = elevator_find_get(q, elevator_name); + if (!e) + return -EINVAL; + } + ret = elevator_switch(q, e); + elevator_put(e); + return ret; +} + +ssize_t elv_iosched_store(struct request_queue *q, const char *buf, + size_t count) +{ + char elevator_name[ELV_NAME_MAX]; + int ret; + + if (!elv_support_iosched(q)) + return count; + + strscpy(elevator_name, buf, sizeof(elevator_name)); + ret = elevator_change(q, strstrip(elevator_name)); + if (!ret) + return count; + return ret; +} + +ssize_t elv_iosched_show(struct request_queue *q, char *name) +{ + struct elevator_queue *eq = q->elevator; + struct elevator_type *cur = NULL, *e; + int len = 0; + + if (!elv_support_iosched(q)) + return sprintf(name, "none\n"); + + if (!q->elevator) { + len += sprintf(name+len, "[none] "); + } else { + len += sprintf(name+len, "none "); + cur = eq->type; + } + + spin_lock(&elv_list_lock); + list_for_each_entry(e, &elv_list, list) { + if (e == cur) + len += sprintf(name+len, "[%s] ", e->elevator_name); + else if (elv_support_features(q, e)) + len += sprintf(name+len, "%s ", e->elevator_name); + } + spin_unlock(&elv_list_lock); + + len += sprintf(name+len, "\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); + +static int __init elevator_setup(char *str) +{ + pr_warn("Kernel parameter elevator= does not have any effect anymore.\n" + "Please use sysfs to set IO scheduler for individual devices.\n"); + return 1; +} + +__setup("elevator=", elevator_setup); |