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851 lines
19 KiB
851 lines
19 KiB
// SPDX-License-Identifier: GPL-2.0 |
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/* |
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* Block device elevator/IO-scheduler. |
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* |
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* Copyright (C) 2000 Andrea Arcangeli <[email protected]> SuSE |
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* |
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* 30042000 Jens Axboe <[email protected]> : |
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* |
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* Split the elevator a bit so that it is possible to choose a different |
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* one or even write a new "plug in". There are three pieces: |
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* - elevator_fn, inserts a new request in the queue list |
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* - elevator_merge_fn, decides whether a new buffer can be merged with |
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* an existing request |
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* - elevator_dequeue_fn, called when a request is taken off the active list |
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* |
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* 20082000 Dave Jones <[email protected]> : |
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* Removed tests for max-bomb-segments, which was breaking elvtune |
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* when run without -bN |
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* |
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* Jens: |
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* - Rework again to work with bio instead of buffer_heads |
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* - loose bi_dev comparisons, partition handling is right now |
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* - completely modularize elevator setup and teardown |
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* |
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*/ |
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#include <linux/kernel.h> |
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#include <linux/fs.h> |
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#include <linux/blkdev.h> |
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#include <linux/elevator.h> |
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#include <linux/bio.h> |
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#include <linux/module.h> |
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#include <linux/slab.h> |
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#include <linux/init.h> |
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#include <linux/compiler.h> |
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#include <linux/blktrace_api.h> |
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#include <linux/hash.h> |
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#include <linux/uaccess.h> |
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#include <linux/pm_runtime.h> |
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#include <linux/blk-cgroup.h> |
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#include <trace/events/block.h> |
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#include "blk.h" |
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#include "blk-mq-sched.h" |
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#include "blk-pm.h" |
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#include "blk-wbt.h" |
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static DEFINE_SPINLOCK(elv_list_lock); |
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static LIST_HEAD(elv_list); |
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|
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/* |
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* Merge hash stuff. |
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*/ |
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#define rq_hash_key(rq) (blk_rq_pos(rq) + blk_rq_sectors(rq)) |
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|
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/* |
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* Query io scheduler to see if the current process issuing bio may be |
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* merged with rq. |
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*/ |
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static int elv_iosched_allow_bio_merge(struct request *rq, struct bio *bio) |
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{ |
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struct request_queue *q = rq->q; |
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struct elevator_queue *e = q->elevator; |
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if (e->type->ops.allow_merge) |
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return e->type->ops.allow_merge(q, rq, bio); |
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return 1; |
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} |
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/* |
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* can we safely merge with this request? |
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*/ |
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bool elv_bio_merge_ok(struct request *rq, struct bio *bio) |
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{ |
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if (!blk_rq_merge_ok(rq, bio)) |
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return false; |
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if (!elv_iosched_allow_bio_merge(rq, bio)) |
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return false; |
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return true; |
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} |
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EXPORT_SYMBOL(elv_bio_merge_ok); |
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static inline bool elv_support_features(unsigned int elv_features, |
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unsigned int required_features) |
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{ |
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return (required_features & elv_features) == required_features; |
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} |
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/** |
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* elevator_match - Test an elevator name and features |
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* @e: Scheduler to test |
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* @name: Elevator name to test |
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* @required_features: Features that the elevator must provide |
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* |
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* Return true if the elevator @e name matches @name and if @e provides all |
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* the features specified by @required_features. |
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*/ |
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static bool elevator_match(const struct elevator_type *e, const char *name, |
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unsigned int required_features) |
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{ |
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if (!elv_support_features(e->elevator_features, required_features)) |
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return false; |
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if (!strcmp(e->elevator_name, name)) |
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return true; |
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if (e->elevator_alias && !strcmp(e->elevator_alias, name)) |
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return true; |
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return false; |
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} |
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/** |
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* elevator_find - Find an elevator |
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* @name: Name of the elevator to find |
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* @required_features: Features that the elevator must provide |
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* |
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* Return the first registered scheduler with name @name and supporting the |
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* features @required_features and NULL otherwise. |
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*/ |
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static struct elevator_type *elevator_find(const char *name, |
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unsigned int required_features) |
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{ |
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struct elevator_type *e; |
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list_for_each_entry(e, &elv_list, list) { |
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if (elevator_match(e, name, required_features)) |
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return e; |
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} |
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return NULL; |
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} |
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static void elevator_put(struct elevator_type *e) |
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{ |
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module_put(e->elevator_owner); |
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} |
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static struct elevator_type *elevator_get(struct request_queue *q, |
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const char *name, bool try_loading) |
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{ |
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struct elevator_type *e; |
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spin_lock(&elv_list_lock); |
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e = elevator_find(name, q->required_elevator_features); |
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if (!e && try_loading) { |
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spin_unlock(&elv_list_lock); |
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request_module("%s-iosched", name); |
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spin_lock(&elv_list_lock); |
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e = elevator_find(name, q->required_elevator_features); |
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} |
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if (e && !try_module_get(e->elevator_owner)) |
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e = NULL; |
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spin_unlock(&elv_list_lock); |
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return e; |
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} |
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static struct kobj_type elv_ktype; |
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struct elevator_queue *elevator_alloc(struct request_queue *q, |
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struct elevator_type *e) |
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{ |
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struct elevator_queue *eq; |
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eq = kzalloc_node(sizeof(*eq), GFP_KERNEL, q->node); |
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if (unlikely(!eq)) |
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return NULL; |
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eq->type = e; |
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kobject_init(&eq->kobj, &elv_ktype); |
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mutex_init(&eq->sysfs_lock); |
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hash_init(eq->hash); |
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return eq; |
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} |
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EXPORT_SYMBOL(elevator_alloc); |
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static void elevator_release(struct kobject *kobj) |
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{ |
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struct elevator_queue *e; |
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e = container_of(kobj, struct elevator_queue, kobj); |
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elevator_put(e->type); |
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kfree(e); |
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} |
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void __elevator_exit(struct request_queue *q, struct elevator_queue *e) |
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{ |
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mutex_lock(&e->sysfs_lock); |
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blk_mq_exit_sched(q, e); |
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mutex_unlock(&e->sysfs_lock); |
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kobject_put(&e->kobj); |
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} |
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static inline void __elv_rqhash_del(struct request *rq) |
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{ |
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hash_del(&rq->hash); |
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rq->rq_flags &= ~RQF_HASHED; |
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} |
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void elv_rqhash_del(struct request_queue *q, struct request *rq) |
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{ |
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if (ELV_ON_HASH(rq)) |
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__elv_rqhash_del(rq); |
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} |
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EXPORT_SYMBOL_GPL(elv_rqhash_del); |
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void elv_rqhash_add(struct request_queue *q, struct request *rq) |
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{ |
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struct elevator_queue *e = q->elevator; |
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BUG_ON(ELV_ON_HASH(rq)); |
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hash_add(e->hash, &rq->hash, rq_hash_key(rq)); |
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rq->rq_flags |= RQF_HASHED; |
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} |
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EXPORT_SYMBOL_GPL(elv_rqhash_add); |
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void elv_rqhash_reposition(struct request_queue *q, struct request *rq) |
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{ |
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__elv_rqhash_del(rq); |
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elv_rqhash_add(q, rq); |
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} |
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struct request *elv_rqhash_find(struct request_queue *q, sector_t offset) |
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{ |
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struct elevator_queue *e = q->elevator; |
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struct hlist_node *next; |
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struct request *rq; |
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hash_for_each_possible_safe(e->hash, rq, next, hash, offset) { |
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BUG_ON(!ELV_ON_HASH(rq)); |
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if (unlikely(!rq_mergeable(rq))) { |
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__elv_rqhash_del(rq); |
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continue; |
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} |
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if (rq_hash_key(rq) == offset) |
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return rq; |
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} |
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return NULL; |
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} |
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/* |
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* RB-tree support functions for inserting/lookup/removal of requests |
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* in a sorted RB tree. |
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*/ |
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void elv_rb_add(struct rb_root *root, struct request *rq) |
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{ |
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struct rb_node **p = &root->rb_node; |
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struct rb_node *parent = NULL; |
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struct request *__rq; |
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while (*p) { |
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parent = *p; |
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__rq = rb_entry(parent, struct request, rb_node); |
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if (blk_rq_pos(rq) < blk_rq_pos(__rq)) |
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p = &(*p)->rb_left; |
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else if (blk_rq_pos(rq) >= blk_rq_pos(__rq)) |
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p = &(*p)->rb_right; |
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} |
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rb_link_node(&rq->rb_node, parent, p); |
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rb_insert_color(&rq->rb_node, root); |
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} |
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EXPORT_SYMBOL(elv_rb_add); |
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void elv_rb_del(struct rb_root *root, struct request *rq) |
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{ |
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BUG_ON(RB_EMPTY_NODE(&rq->rb_node)); |
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rb_erase(&rq->rb_node, root); |
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RB_CLEAR_NODE(&rq->rb_node); |
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} |
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EXPORT_SYMBOL(elv_rb_del); |
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struct request *elv_rb_find(struct rb_root *root, sector_t sector) |
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{ |
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struct rb_node *n = root->rb_node; |
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struct request *rq; |
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while (n) { |
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rq = rb_entry(n, struct request, rb_node); |
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if (sector < blk_rq_pos(rq)) |
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n = n->rb_left; |
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else if (sector > blk_rq_pos(rq)) |
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n = n->rb_right; |
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else |
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return rq; |
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} |
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return NULL; |
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} |
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EXPORT_SYMBOL(elv_rb_find); |
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enum elv_merge elv_merge(struct request_queue *q, struct request **req, |
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struct bio *bio) |
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{ |
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struct elevator_queue *e = q->elevator; |
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struct request *__rq; |
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/* |
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* Levels of merges: |
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* nomerges: No merges at all attempted |
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* noxmerges: Only simple one-hit cache try |
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* merges: All merge tries attempted |
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*/ |
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if (blk_queue_nomerges(q) || !bio_mergeable(bio)) |
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return ELEVATOR_NO_MERGE; |
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/* |
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* First try one-hit cache. |
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*/ |
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if (q->last_merge && elv_bio_merge_ok(q->last_merge, bio)) { |
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enum elv_merge ret = blk_try_merge(q->last_merge, bio); |
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if (ret != ELEVATOR_NO_MERGE) { |
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*req = q->last_merge; |
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return ret; |
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} |
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} |
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if (blk_queue_noxmerges(q)) |
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return ELEVATOR_NO_MERGE; |
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/* |
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* See if our hash lookup can find a potential backmerge. |
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*/ |
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__rq = elv_rqhash_find(q, bio->bi_iter.bi_sector); |
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if (__rq && elv_bio_merge_ok(__rq, bio)) { |
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*req = __rq; |
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if (blk_discard_mergable(__rq)) |
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return ELEVATOR_DISCARD_MERGE; |
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return ELEVATOR_BACK_MERGE; |
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} |
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if (e->type->ops.request_merge) |
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return e->type->ops.request_merge(q, req, bio); |
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return ELEVATOR_NO_MERGE; |
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} |
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/* |
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* Attempt to do an insertion back merge. Only check for the case where |
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* we can append 'rq' to an existing request, so we can throw 'rq' away |
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* afterwards. |
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* |
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* Returns true if we merged, false otherwise. 'free' will contain all |
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* requests that need to be freed. |
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*/ |
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bool elv_attempt_insert_merge(struct request_queue *q, struct request *rq, |
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struct list_head *free) |
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{ |
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struct request *__rq; |
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bool ret; |
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if (blk_queue_nomerges(q)) |
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return false; |
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/* |
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* First try one-hit cache. |
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*/ |
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if (q->last_merge && blk_attempt_req_merge(q, q->last_merge, rq)) { |
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list_add(&rq->queuelist, free); |
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return true; |
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} |
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if (blk_queue_noxmerges(q)) |
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return false; |
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ret = false; |
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/* |
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* See if our hash lookup can find a potential backmerge. |
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*/ |
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while (1) { |
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__rq = elv_rqhash_find(q, blk_rq_pos(rq)); |
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if (!__rq || !blk_attempt_req_merge(q, __rq, rq)) |
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break; |
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list_add(&rq->queuelist, free); |
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/* The merged request could be merged with others, try again */ |
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ret = true; |
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rq = __rq; |
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} |
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return ret; |
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} |
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void elv_merged_request(struct request_queue *q, struct request *rq, |
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enum elv_merge type) |
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{ |
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struct elevator_queue *e = q->elevator; |
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if (e->type->ops.request_merged) |
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e->type->ops.request_merged(q, rq, type); |
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if (type == ELEVATOR_BACK_MERGE) |
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elv_rqhash_reposition(q, rq); |
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q->last_merge = rq; |
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} |
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void elv_merge_requests(struct request_queue *q, struct request *rq, |
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struct request *next) |
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{ |
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struct elevator_queue *e = q->elevator; |
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if (e->type->ops.requests_merged) |
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e->type->ops.requests_merged(q, rq, next); |
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elv_rqhash_reposition(q, rq); |
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q->last_merge = rq; |
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} |
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struct request *elv_latter_request(struct request_queue *q, struct request *rq) |
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{ |
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struct elevator_queue *e = q->elevator; |
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if (e->type->ops.next_request) |
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return e->type->ops.next_request(q, rq); |
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return NULL; |
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} |
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struct request *elv_former_request(struct request_queue *q, struct request *rq) |
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{ |
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struct elevator_queue *e = q->elevator; |
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if (e->type->ops.former_request) |
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return e->type->ops.former_request(q, rq); |
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return NULL; |
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} |
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#define to_elv(atr) container_of((atr), struct elv_fs_entry, attr) |
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static ssize_t |
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elv_attr_show(struct kobject *kobj, struct attribute *attr, char *page) |
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{ |
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struct elv_fs_entry *entry = to_elv(attr); |
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struct elevator_queue *e; |
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ssize_t error; |
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if (!entry->show) |
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return -EIO; |
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e = container_of(kobj, struct elevator_queue, kobj); |
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mutex_lock(&e->sysfs_lock); |
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error = e->type ? entry->show(e, page) : -ENOENT; |
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mutex_unlock(&e->sysfs_lock); |
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return error; |
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} |
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static ssize_t |
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elv_attr_store(struct kobject *kobj, struct attribute *attr, |
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const char *page, size_t length) |
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{ |
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struct elv_fs_entry *entry = to_elv(attr); |
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struct elevator_queue *e; |
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ssize_t error; |
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if (!entry->store) |
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return -EIO; |
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e = container_of(kobj, struct elevator_queue, kobj); |
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mutex_lock(&e->sysfs_lock); |
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error = e->type ? entry->store(e, page, length) : -ENOENT; |
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mutex_unlock(&e->sysfs_lock); |
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return error; |
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} |
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static const struct sysfs_ops elv_sysfs_ops = { |
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.show = elv_attr_show, |
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.store = elv_attr_store, |
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}; |
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static struct kobj_type elv_ktype = { |
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.sysfs_ops = &elv_sysfs_ops, |
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.release = elevator_release, |
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}; |
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int elv_register_queue(struct request_queue *q, bool uevent) |
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{ |
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struct elevator_queue *e = q->elevator; |
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int error; |
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lockdep_assert_held(&q->sysfs_lock); |
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error = kobject_add(&e->kobj, &q->kobj, "%s", "iosched"); |
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if (!error) { |
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struct elv_fs_entry *attr = e->type->elevator_attrs; |
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if (attr) { |
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while (attr->attr.name) { |
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if (sysfs_create_file(&e->kobj, &attr->attr)) |
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break; |
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attr++; |
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} |
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} |
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if (uevent) |
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kobject_uevent(&e->kobj, KOBJ_ADD); |
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e->registered = 1; |
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} |
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return error; |
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} |
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void elv_unregister_queue(struct request_queue *q) |
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{ |
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lockdep_assert_held(&q->sysfs_lock); |
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if (q) { |
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struct elevator_queue *e = q->elevator; |
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kobject_uevent(&e->kobj, KOBJ_REMOVE); |
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kobject_del(&e->kobj); |
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e->registered = 0; |
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/* Re-enable throttling in case elevator disabled it */ |
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wbt_enable_default(q); |
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} |
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} |
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int elv_register(struct elevator_type *e) |
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{ |
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/* insert_requests and dispatch_request are mandatory */ |
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if (WARN_ON_ONCE(!e->ops.insert_requests || !e->ops.dispatch_request)) |
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return -EINVAL; |
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|
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/* create icq_cache if requested */ |
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if (e->icq_size) { |
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if (WARN_ON(e->icq_size < sizeof(struct io_cq)) || |
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WARN_ON(e->icq_align < __alignof__(struct io_cq))) |
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return -EINVAL; |
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snprintf(e->icq_cache_name, sizeof(e->icq_cache_name), |
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"%s_io_cq", e->elevator_name); |
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e->icq_cache = kmem_cache_create(e->icq_cache_name, e->icq_size, |
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e->icq_align, 0, NULL); |
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if (!e->icq_cache) |
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return -ENOMEM; |
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} |
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/* register, don't allow duplicate names */ |
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spin_lock(&elv_list_lock); |
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if (elevator_find(e->elevator_name, 0)) { |
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spin_unlock(&elv_list_lock); |
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kmem_cache_destroy(e->icq_cache); |
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return -EBUSY; |
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} |
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list_add_tail(&e->list, &elv_list); |
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spin_unlock(&elv_list_lock); |
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printk(KERN_INFO "io scheduler %s registered\n", e->elevator_name); |
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return 0; |
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} |
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EXPORT_SYMBOL_GPL(elv_register); |
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|
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void elv_unregister(struct elevator_type *e) |
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{ |
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/* unregister */ |
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spin_lock(&elv_list_lock); |
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list_del_init(&e->list); |
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spin_unlock(&elv_list_lock); |
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|
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/* |
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* Destroy icq_cache if it exists. icq's are RCU managed. Make |
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* sure all RCU operations are complete before proceeding. |
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*/ |
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if (e->icq_cache) { |
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rcu_barrier(); |
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kmem_cache_destroy(e->icq_cache); |
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e->icq_cache = NULL; |
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} |
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} |
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EXPORT_SYMBOL_GPL(elv_unregister); |
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|
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int elevator_switch_mq(struct request_queue *q, |
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struct elevator_type *new_e) |
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{ |
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int ret; |
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|
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lockdep_assert_held(&q->sysfs_lock); |
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|
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if (q->elevator) { |
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if (q->elevator->registered) |
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elv_unregister_queue(q); |
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|
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ioc_clear_queue(q); |
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elevator_exit(q, q->elevator); |
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} |
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|
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ret = blk_mq_init_sched(q, new_e); |
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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; |
|
} |
|
|
|
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_sbitmap_shared(q->tag_set->flags)) |
|
return NULL; |
|
|
|
return elevator_get(q, "mq-deadline", false); |
|
} |
|
|
|
/* |
|
* 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(e->elevator_features, |
|
q->required_elevator_features)) { |
|
found = e; |
|
break; |
|
} |
|
} |
|
|
|
if (found && !try_module_get(found->elevator_owner)) |
|
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; |
|
|
|
blk_mq_freeze_queue(q); |
|
blk_mq_quiesce_queue(q); |
|
|
|
err = blk_mq_init_sched(q, e); |
|
|
|
blk_mq_unquiesce_queue(q); |
|
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. 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, 0)) { |
|
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 (!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, 0)) { |
|
len += sprintf(name+len, "[%s] ", elv->elevator_name); |
|
continue; |
|
} |
|
if (elv_support_iosched(q) && |
|
elevator_match(__e, __e->elevator_name, |
|
q->required_elevator_features)) |
|
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); |
|
|
|
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);
|
|
|