// SPDX-License-Identifier: GPL-2.0/* *  Block device elevator/IO-scheduler. * *  Copyright (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE * * 30042000 Jens Axboe <axboe@kernel.dk> : * * Split the elevator a bit so that it is possible to choose a different * one or even write a new "plug in". There are three pieces: * - elevator_fn, inserts a new request in the queue list * - elevator_merge_fn, decides whether a new buffer can be merged with *   an existing request * - elevator_dequeue_fn, called when a request is taken off the active list * * 20082000 Dave Jones <davej@suse.de> : * Removed tests for max-bomb-segments, which was breaking elvtune *  when run without -bN * * Jens: * - Rework again to work with bio instead of buffer_heads * - loose bi_dev comparisons, partition handling is right now * - completely modularize elevator setup and teardown * */#include <linux/kernel.h>#include <linux/fs.h>#include <linux/blkdev.h>#include <linux/bio.h>#include <linux/module.h>#include <linux/slab.h>#include <linux/init.h>#include <linux/compiler.h>#include <linux/blktrace_api.h>#include <linux/hash.h>#include <linux/uaccess.h>#include <linux/pm_runtime.h> #include <trace/events/block.h> #include "elevator.h"#include "blk.h"#include "blk-mq-sched.h"#include "blk-pm.h"#include "blk-wbt.h"#include "blk-cgroup.h" static DEFINE_SPINLOCK(elv_list_lock);static LIST_HEAD(elv_list); /* * Merge hash stuff. */#define rq_hash_key(rq)		(blk_rq_pos(rq) + blk_rq_sectors(rq)) /* * Query io scheduler to see if the current process issuing bio may be * merged with rq. */static bool elv_iosched_allow_bio_merge(struct request *rq, struct bio *bio){	struct request_queue *q = rq->q;	struct elevator_queue *e = q->elevator; 	if (e->type->ops.allow_merge)		return e->type->ops.allow_merge(q, rq, bio); 	return true;} /* * can we safely merge with this request? */bool elv_bio_merge_ok(struct request *rq, struct bio *bio){	if (!blk_rq_merge_ok(rq, bio))		return false; 	if (!elv_iosched_allow_bio_merge(rq, bio))		return false; 	return true;}EXPORT_SYMBOL(elv_bio_merge_ok); /** * elevator_match - Check whether @e's name or alias matches @name * @e: Scheduler to test * @name: Elevator name to test * * Return true if the elevator @e's name or alias matches @name. */static bool elevator_match(const struct elevator_type *e, const char *name){	return !strcmp(e->elevator_name, name) ||		(e->elevator_alias && !strcmp(e->elevator_alias, name));} static struct elevator_type *__elevator_find(const char *name){	struct elevator_type *e; 	list_for_each_entry(e, &elv_list, list)		if (elevator_match(e, name))			return e;	return NULL;} static struct elevator_type *elevator_find_get(const char *name){	struct elevator_type *e; 	spin_lock(&elv_list_lock);	e = __elevator_find(name);	if (e && (!elevator_tryget(e)))		e = NULL;	spin_unlock(&elv_list_lock);	return e;} static const struct kobj_type elv_ktype; struct elevator_queue *elevator_alloc(struct request_queue *q,		struct elevator_type *e, struct elevator_resources *res){	struct elevator_queue *eq; 	eq = kzalloc_node(sizeof(*eq), GFP_KERNEL, q->node);	if (unlikely(!eq))		return NULL; 	__elevator_get(e);	eq->type = e;	kobject_init(&eq->kobj, &elv_ktype);	mutex_init(&eq->sysfs_lock);	hash_init(eq->hash);	eq->et = res->et;	eq->elevator_data = res->data; 	return eq;} 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);} static void elevator_exit(struct request_queue *q){	struct elevator_queue *e = q->elevator; 	lockdep_assert_held(&q->elevator_lock); 	ioc_clear_queue(q); 	mutex_lock(&e->sysfs_lock);	blk_mq_exit_sched(q, e);	mutex_unlock(&e->sysfs_lock);} static inline void __elv_rqhash_del(struct request *rq){	hash_del(&rq->hash);	rq->rq_flags &= ~RQF_HASHED;} void elv_rqhash_del(struct request_queue *q, struct request *rq){	if (ELV_ON_HASH(rq))		__elv_rqhash_del(rq);}EXPORT_SYMBOL_GPL(elv_rqhash_del); void elv_rqhash_add(struct request_queue *q, struct request *rq){	struct elevator_queue *e = q->elevator; 	BUG_ON(ELV_ON_HASH(rq));	hash_add(e->hash, &rq->hash, rq_hash_key(rq));	rq->rq_flags |= RQF_HASHED;}EXPORT_SYMBOL_GPL(elv_rqhash_add); void elv_rqhash_reposition(struct request_queue *q, struct request *rq){	__elv_rqhash_del(rq);	elv_rqhash_add(q, rq);} struct request *elv_rqhash_find(struct request_queue *q, sector_t offset){	struct elevator_queue *e = q->elevator;	struct hlist_node *next;	struct request *rq; 	hash_for_each_possible_safe(e->hash, rq, next, hash, offset) {		BUG_ON(!ELV_ON_HASH(rq)); 		if (unlikely(!rq_mergeable(rq))) {			__elv_rqhash_del(rq);			continue;		} 		if (rq_hash_key(rq) == offset)			return rq;	} 	return NULL;} /* * RB-tree support functions for inserting/lookup/removal of requests * in a sorted RB tree. */void elv_rb_add(struct rb_root *root, struct request *rq){	struct rb_node **p = &root->rb_node;	struct rb_node *parent = NULL;	struct request *__rq; 	while (*p) {		parent = *p;		__rq = rb_entry(parent, struct request, rb_node); 		if (blk_rq_pos(rq) < blk_rq_pos(__rq))			p = &(*p)->rb_left;		else if (blk_rq_pos(rq) >= blk_rq_pos(__rq))			p = &(*p)->rb_right;	} 	rb_link_node(&rq->rb_node, parent, p);	rb_insert_color(&rq->rb_node, root);}EXPORT_SYMBOL(elv_rb_add); void elv_rb_del(struct rb_root *root, struct request *rq){	BUG_ON(RB_EMPTY_NODE(&rq->rb_node));	rb_erase(&rq->rb_node, root);	RB_CLEAR_NODE(&rq->rb_node);}EXPORT_SYMBOL(elv_rb_del); struct request *elv_rb_find(struct rb_root *root, sector_t sector){	struct rb_node *n = root->rb_node;	struct request *rq; 	while (n) {		rq = rb_entry(n, struct request, rb_node); 		if (sector < blk_rq_pos(rq))			n = n->rb_left;		else if (sector > blk_rq_pos(rq))			n = n->rb_right;		else			return rq;	} 	return NULL;}EXPORT_SYMBOL(elv_rb_find); enum elv_merge elv_merge(struct request_queue *q, struct request **req,		struct bio *bio){	struct elevator_queue *e = q->elevator;	struct request *__rq; 	/*	 * Levels of merges:	 * 	nomerges:  No merges at all attempted	 * 	noxmerges: Only simple one-hit cache try	 * 	merges:	   All merge tries attempted	 */	if (blk_queue_nomerges(q) || !bio_mergeable(bio))		return ELEVATOR_NO_MERGE; 	/*	 * First try one-hit cache.	 */	if (q->last_merge && elv_bio_merge_ok(q->last_merge, bio)) {		enum elv_merge ret = blk_try_merge(q->last_merge, bio); 		if (ret != ELEVATOR_NO_MERGE) {			*req = q->last_merge;			return ret;		}	} 	if (blk_queue_noxmerges(q))		return ELEVATOR_NO_MERGE; 	/*	 * See if our hash lookup can find a potential backmerge.	 */	__rq = elv_rqhash_find(q, bio->bi_iter.bi_sector);	if (__rq && elv_bio_merge_ok(__rq, bio)) {		*req = __rq; 		if (blk_discard_mergable(__rq))			return ELEVATOR_DISCARD_MERGE;		return ELEVATOR_BACK_MERGE;	} 	if (e->type->ops.request_merge)		return e->type->ops.request_merge(q, req, bio); 	return ELEVATOR_NO_MERGE;} /* * Attempt to do an insertion back merge. Only check for the case where * we can append 'rq' to an existing request, so we can throw 'rq' away * afterwards. * * Returns true if we merged, false otherwise. 'free' will contain all * requests that need to be freed. */bool elv_attempt_insert_merge(struct request_queue *q, struct request *rq,			      struct list_head *free){	struct request *__rq;	bool ret; 	if (blk_queue_nomerges(q))		return false; 	/*	 * First try one-hit cache.	 */	if (q->last_merge && blk_attempt_req_merge(q, q->last_merge, rq)) {		list_add(&rq->queuelist, free);		return true;	} 	if (blk_queue_noxmerges(q))		return false; 	ret = false;	/*	 * See if our hash lookup can find a potential backmerge.	 */	while (1) {		__rq = elv_rqhash_find(q, blk_rq_pos(rq));		if (!__rq || !blk_attempt_req_merge(q, __rq, rq))			break; 		list_add(&rq->queuelist, free);		/* The merged request could be merged with others, try again */		ret = true;		rq = __rq;	} 	return ret;} void elv_merged_request(struct request_queue *q, struct request *rq,		enum elv_merge type){	struct elevator_queue *e = q->elevator; 	if (e->type->ops.request_merged)		e->type->ops.request_merged(q, rq, type); 	if (type == ELEVATOR_BACK_MERGE)		elv_rqhash_reposition(q, rq); 	q->last_merge = rq;} void elv_merge_requests(struct request_queue *q, struct request *rq,			     struct request *next){	struct elevator_queue *e = q->elevator; 	if (e->type->ops.requests_merged)		e->type->ops.requests_merged(q, rq, next); 	elv_rqhash_reposition(q, rq);	q->last_merge = rq;} struct request *elv_latter_request(struct request_queue *q, struct request *rq){	struct elevator_queue *e = q->elevator; 	if (e->type->ops.next_request)		return e->type->ops.next_request(q, rq); 	return NULL;} struct request *elv_former_request(struct request_queue *q, struct request *rq){	struct elevator_queue *e = q->elevator; 	if (e->type->ops.former_request)		return e->type->ops.former_request(q, rq); 	return NULL;} #define to_elv(atr) container_of_const((atr), struct elv_fs_entry, attr) static ssize_telv_attr_show(struct kobject *kobj, struct attribute *attr, char *page){	const struct elv_fs_entry *entry = to_elv(attr);	struct elevator_queue *e;	ssize_t error = -ENODEV; 	if (!entry->show)		return -EIO; 	e = container_of(kobj, struct elevator_queue, kobj);	mutex_lock(&e->sysfs_lock);	if (!test_bit(ELEVATOR_FLAG_DYING, &e->flags))		error = entry->show(e, page);	mutex_unlock(&e->sysfs_lock);	return error;} static ssize_telv_attr_store(struct kobject *kobj, struct attribute *attr,	       const char *page, size_t length){	const struct elv_fs_entry *entry = to_elv(attr);	struct elevator_queue *e;	ssize_t error = -ENODEV; 	if (!entry->store)		return -EIO; 	e = container_of(kobj, struct elevator_queue, kobj);	mutex_lock(&e->sysfs_lock);	if (!test_bit(ELEVATOR_FLAG_DYING, &e->flags))		error = entry->store(e, page, length);	mutex_unlock(&e->sysfs_lock);	return error;} static const struct sysfs_ops elv_sysfs_ops = {	.show	= elv_attr_show,	.store	= elv_attr_store,}; static const struct kobj_type elv_ktype = {	.sysfs_ops	= &elv_sysfs_ops,	.release	= elevator_release,}; static int elv_register_queue(struct request_queue *q,			      struct elevator_queue *e,			      bool uevent){	int error; 	error = kobject_add(&e->kobj, &q->disk->queue_kobj, "iosched");	if (!error) {		const 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); 		/*		 * Sched is initialized, it is ready to export it via		 * debugfs		 */		blk_mq_sched_reg_debugfs(q);		set_bit(ELEVATOR_FLAG_REGISTERED, &e->flags);	}	return error;} static void elv_unregister_queue(struct request_queue *q,				 struct elevator_queue *e){	if (e && test_and_clear_bit(ELEVATOR_FLAG_REGISTERED, &e->flags)) {		kobject_uevent(&e->kobj, KOBJ_REMOVE);		kobject_del(&e->kobj); 		/* unexport via debugfs before exiting sched */		blk_mq_sched_unreg_debugfs(q);	}} int elv_register(struct elevator_type *e){	/* finish request is mandatory */

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