| // 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/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-pm.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->type->ops.allow_merge) |
| return e->type->ops.allow_merge(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' |
| */ |
| 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 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); |
| if (!e && try_loading) { |
| 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 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); |
| |
| 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) |
| { |
| mutex_lock(&e->sysfs_lock); |
| if (e->type->ops.exit_sched) |
| 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; |
| 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 |
| */ |
| 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->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 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); |
| |
| mutex_lock(&q->sysfs_lock); |
| e->registered = 1; |
| mutex_unlock(&q->sysfs_lock); |
| } |
| 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); |
| |
| mutex_lock(&q->sysfs_lock); |
| e->registered = 0; |
| /* Re-enable throttling in case elevator disabled it */ |
| wbt_enable_default(q); |
| mutex_unlock(&q->sysfs_lock); |
| } |
| } |
| |
| int elv_register(struct elevator_type *e) |
| { |
| /* 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); |
| |
| 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) { |
| mutex_unlock(&q->sysfs_lock); |
| |
| /* |
| * Concurrent elevator switch can't happen becasue |
| * sysfs write is always exclusively on same file. |
| * |
| * Also the elevator queue won't be freed after |
| * sysfs_lock is released becasue kobject_del() in |
| * blk_unregister_queue() waits for completion of |
| * .store & .show on its attributes. |
| */ |
| elv_unregister_queue(q); |
| |
| mutex_lock(&q->sysfs_lock); |
| } |
| ioc_clear_queue(q); |
| elevator_exit(q, q->elevator); |
| |
| /* |
| * sysfs_lock may be dropped, so re-check if queue is |
| * unregistered. If yes, don't switch to new elevator |
| * any more |
| */ |
| if (!blk_queue_registered(q)) |
| return 0; |
| } |
| |
| ret = blk_mq_init_sched(q, new_e); |
| if (ret) |
| goto out; |
| |
| if (new_e) { |
| mutex_unlock(&q->sysfs_lock); |
| |
| ret = elv_register_queue(q, true); |
| |
| mutex_lock(&q->sysfs_lock); |
| 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; |
| } |
| |
| static inline bool elv_support_iosched(struct request_queue *q) |
| { |
| if (q->tag_set && (q->tag_set->flags & BLK_MQ_F_NO_SCHED)) |
| return false; |
| return true; |
| } |
| |
| /* |
| * For blk-mq devices supporting IO scheduling, 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 (!elv_support_iosched(q)) |
| return 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) |
| { |
| int err; |
| |
| lockdep_assert_held(&q->sysfs_lock); |
| |
| 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; |
| } |
| |
| /* |
| * 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 (!strncmp(name, "none", 4)) { |
| if (!q->elevator) |
| return 0; |
| 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); |
| } |
| |
| ssize_t elv_iosched_store(struct request_queue *q, const char *name, |
| size_t count) |
| { |
| int ret; |
| |
| if (!queue_is_mq(q) || !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; |
| int len = 0; |
| |
| if (!queue_is_mq(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)) { |
| len += sprintf(name+len, "[%s] ", elv->elevator_name); |
| continue; |
| } |
| if (elv_support_iosched(q)) |
| len += sprintf(name+len, "%s ", __e->elevator_name); |
| } |
| spin_unlock(&elv_list_lock); |
| |
| if (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); |