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![Christoph Hellwig](/assets/img/avatar_default.png)
All callers pass q->elevator. Signed-off-by: Christoph Hellwig <hch@lst.de> Link: https://lore.kernel.org/r/20211123185312.1432157-4-hch@lst.de Signed-off-by: Jens Axboe <axboe@kernel.dk>
861 lines
19 KiB
C
861 lines
19 KiB
C
// 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 <andrea@suse.de> SuSE
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*
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* 30042000 Jens Axboe <axboe@kernel.dk> :
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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 <davej@suse.de> :
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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/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 "elevator.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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* 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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* 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)
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{
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struct elevator_queue *e = q->elevator;
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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 */
|
|
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, 0)) {
|
|
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)
|
|
elv_unregister_queue(q);
|
|
|
|
ioc_clear_queue(q);
|
|
blk_mq_sched_free_rqs(q);
|
|
elevator_exit(q);
|
|
}
|
|
|
|
ret = blk_mq_init_sched(q, new_e);
|
|
if (ret)
|
|
goto out;
|
|
|
|
if (new_e) {
|
|
ret = elv_register_queue(q, true);
|
|
if (ret) {
|
|
blk_mq_sched_free_rqs(q);
|
|
elevator_exit(q);
|
|
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_shared_tags(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;
|
|
|
|
/*
|
|
* 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. 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);
|