/* *  Block device elevator/IO-scheduler. * *  Copyright (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE * * 30042000 Jens Axboe <axboe@kernel.dk> : * * Split the elevator a bit so that it is possible to choose a different * one or even write a new "plug in". There are three pieces: * - elevator_fn, inserts a new request in the queue list * - elevator_merge_fn, decides whether a new buffer can be merged with *   an existing request * - elevator_dequeue_fn, called when a request is taken off the active list * * 20082000 Dave Jones <davej@suse.de> : * Removed tests for max-bomb-segments, which was breaking elvtune *  when run without -bN * * Jens: * - Rework again to work with bio instead of buffer_heads * - loose bi_dev comparisons, partition handling is right now * - completely modularize elevator setup and teardown * */#include <linux/kernel.h>#include <linux/fs.h>#include <linux/blkdev.h>#include <linux/elevator.h>#include <linux/bio.h>#include <linux/module.h>#include <linux/slab.h>#include <linux/init.h>#include <linux/compiler.h>#include <linux/delay.h>#include <linux/blktrace_api.h>#include <linux/hash.h> #include <asm/uaccess.h> static DEFINE_SPINLOCK(elv_list_lock);static LIST_HEAD(elv_list); /* * Merge hash stuff. */static const int elv_hash_shift = 6;#define ELV_HASH_BLOCK(sec)	((sec) >> 3)#define ELV_HASH_FN(sec)	(hash_long(ELV_HASH_BLOCK((sec)), elv_hash_shift))#define ELV_HASH_ENTRIES	(1 << elv_hash_shift)#define rq_hash_key(rq)		((rq)->sector + (rq)->nr_sectors)#define ELV_ON_HASH(rq)		(!hlist_unhashed(&(rq)->hash)) /* * Query io scheduler to see if the current process issuing bio may be * merged with rq. */static int elv_iosched_allow_merge(struct request *rq, struct bio *bio){	request_queue_t *q = rq->q;	elevator_t *e = q->elevator; 	if (e->ops->elevator_allow_merge_fn)		return e->ops->elevator_allow_merge_fn(q, rq, bio); 	return 1;} /* * can we safely merge with this request? */inline int elv_rq_merge_ok(struct request *rq, struct bio *bio){	if (!rq_mergeable(rq))		return 0; 	/*	 * different data direction or already started, don't merge	 */	if (bio_data_dir(bio) != rq_data_dir(rq))		return 0; 	/*	 * must be same device and not a special request	 */	if (rq->rq_disk != bio->bi_bdev->bd_disk || rq->special)		return 0; 	if (!elv_iosched_allow_merge(rq, bio))		return 0; 	return 1;}EXPORT_SYMBOL(elv_rq_merge_ok); static inline int elv_try_merge(struct request *__rq, struct bio *bio){	int ret = ELEVATOR_NO_MERGE; 	/*	 * we can merge and sequence is ok, check if it's possible	 */	if (elv_rq_merge_ok(__rq, bio)) {		if (__rq->sector + __rq->nr_sectors == bio->bi_sector)			ret = ELEVATOR_BACK_MERGE;		else if (__rq->sector - bio_sectors(bio) == bio->bi_sector)			ret = ELEVATOR_FRONT_MERGE;	} 	return ret;} static struct elevator_type *elevator_find(const char *name){	struct elevator_type *e;	struct list_head *entry; 	list_for_each(entry, &elv_list) { 		e = list_entry(entry, struct elevator_type, list); 		if (!strcmp(e->elevator_name, name))			return e;	} 	return NULL;} static void elevator_put(struct elevator_type *e){	module_put(e->elevator_owner);} static struct elevator_type *elevator_get(const char *name){	struct elevator_type *e; 	spin_lock_irq(&elv_list_lock); 	e = elevator_find(name);	if (e && !try_module_get(e->elevator_owner))		e = NULL; 	spin_unlock_irq(&elv_list_lock); 	return e;} static void *elevator_init_queue(request_queue_t *q, struct elevator_queue *eq){	return eq->ops->elevator_init_fn(q);} static void elevator_attach(request_queue_t *q, struct elevator_queue *eq,			   void *data){	q->elevator = eq;	eq->elevator_data = data;} static char chosen_elevator[16]; static int __init elevator_setup(char *str){	/*	 * Be backwards-compatible with previous kernels, so users	 * won't get the wrong elevator.	 */	if (!strcmp(str, "as"))		strcpy(chosen_elevator, "anticipatory");	else		strncpy(chosen_elevator, str, sizeof(chosen_elevator) - 1);	return 1;} __setup("elevator=", elevator_setup); static struct kobj_type elv_ktype; static elevator_t *elevator_alloc(request_queue_t *q, struct elevator_type *e){	elevator_t *eq;	int i; 	eq = kmalloc_node(sizeof(elevator_t), GFP_KERNEL, q->node);	if (unlikely(!eq))		goto err; 	memset(eq, 0, sizeof(*eq));	eq->ops = &e->ops;	eq->elevator_type = e;	kobject_init(&eq->kobj);	snprintf(eq->kobj.name, KOBJ_NAME_LEN, "%s", "iosched");	eq->kobj.ktype = &elv_ktype;	mutex_init(&eq->sysfs_lock); 	eq->hash = kmalloc_node(sizeof(struct hlist_head) * ELV_HASH_ENTRIES,					GFP_KERNEL, q->node);	if (!eq->hash)		goto err; 	for (i = 0; i < ELV_HASH_ENTRIES; i++)		INIT_HLIST_HEAD(&eq->hash[i]); 	return eq;err:	kfree(eq);	elevator_put(e);	return NULL;} static void elevator_release(struct kobject *kobj){	elevator_t *e = container_of(kobj, elevator_t, kobj); 	elevator_put(e->elevator_type);	kfree(e->hash);	kfree(e);} int elevator_init(request_queue_t *q, char *name){	struct elevator_type *e = NULL;	struct elevator_queue *eq;	int ret = 0;	void *data; 	INIT_LIST_HEAD(&q->queue_head);	q->last_merge = NULL;	q->end_sector = 0;	q->boundary_rq = NULL; 	if (name && !(e = elevator_get(name)))		return -EINVAL; 	if (!e && *chosen_elevator && !(e = elevator_get(chosen_elevator)))		printk("I/O scheduler %s not found\n", chosen_elevator); 	if (!e && !(e = elevator_get(CONFIG_DEFAULT_IOSCHED))) {		printk("Default I/O scheduler not found, using no-op\n");		e = elevator_get("noop");	} 	eq = elevator_alloc(q, e);	if (!eq)		return -ENOMEM; 	data = elevator_init_queue(q, eq);	if (!data) {		kobject_put(&eq->kobj);		return -ENOMEM;	} 	elevator_attach(q, eq, data);	return ret;} EXPORT_SYMBOL(elevator_init); void elevator_exit(elevator_t *e){	mutex_lock(&e->sysfs_lock);	if (e->ops->elevator_exit_fn)		e->ops->elevator_exit_fn(e);	e->ops = NULL;	mutex_unlock(&e->sysfs_lock); 	kobject_put(&e->kobj);} EXPORT_SYMBOL(elevator_exit); static void elv_activate_rq(request_queue_t *q, struct request *rq){	elevator_t *e = q->elevator; 	if (e->ops->elevator_activate_req_fn)		e->ops->elevator_activate_req_fn(q, rq);} static void elv_deactivate_rq(request_queue_t *q, struct request *rq){	elevator_t *e = q->elevator; 	if (e->ops->elevator_deactivate_req_fn)		e->ops->elevator_deactivate_req_fn(q, rq);} static inline void __elv_rqhash_del(struct request *rq){	hlist_del_init(&rq->hash);} static void elv_rqhash_del(request_queue_t *q, struct request *rq){	if (ELV_ON_HASH(rq))		__elv_rqhash_del(rq);} static void elv_rqhash_add(request_queue_t *q, struct request *rq){	elevator_t *e = q->elevator; 	BUG_ON(ELV_ON_HASH(rq));	hlist_add_head(&rq->hash, &e->hash[ELV_HASH_FN(rq_hash_key(rq))]);} static void elv_rqhash_reposition(request_queue_t *q, struct request *rq){	__elv_rqhash_del(rq);	elv_rqhash_add(q, rq);} static struct request *elv_rqhash_find(request_queue_t *q, sector_t offset){	elevator_t *e = q->elevator;	struct hlist_head *hash_list = &e->hash[ELV_HASH_FN(offset)];	struct hlist_node *entry, *next;	struct request *rq; 	hlist_for_each_entry_safe(rq, entry, next, hash_list, hash) {		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. */struct request *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 (rq->sector < __rq->sector)			p = &(*p)->rb_left;		else if (rq->sector > __rq->sector)			p = &(*p)->rb_right;		else			return __rq;	} 	rb_link_node(&rq->rb_node, parent, p);	rb_insert_color(&rq->rb_node, root);	return NULL;} 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 < rq->sector)			n = n->rb_left;		else if (sector > rq->sector)			n = n->rb_right;		else			return rq;	} 	return NULL;} EXPORT_SYMBOL(elv_rb_find); /* * Insert rq into dispatch queue of q.  Queue lock must be held on * entry.  rq is sort insted into the dispatch queue. To be used by * specific elevators. */void elv_dispatch_sort(request_queue_t *q, struct request *rq){	sector_t boundary;	struct list_head *entry; 	if (q->last_merge == rq)		q->last_merge = NULL; 	elv_rqhash_del(q, rq); 	q->nr_sorted--; 	boundary = q->end_sector; 	list_for_each_prev(entry, &q->queue_head) {		struct request *pos = list_entry_rq(entry); 		if (rq_data_dir(rq) != rq_data_dir(pos))			break;		if (pos->cmd_flags & (REQ_SOFTBARRIER|REQ_HARDBARRIER|REQ_STARTED))			break;		if (rq->sector >= boundary) {			if (pos->sector < boundary)				continue;		} else {			if (pos->sector >= boundary)				break;		}		if (rq->sector >= pos->sector)			break;	} 	list_add(&rq->queuelist, entry);} EXPORT_SYMBOL(elv_dispatch_sort); /* * Insert rq into dispatch queue of q.  Queue lock must be held on * entry.  rq is added to the back of the dispatch queue. To be used by * specific elevators. */void elv_dispatch_add_tail(struct request_queue *q, struct request *rq){	if (q->last_merge == rq)		q->last_merge = NULL; 	elv_rqhash_del(q, rq); 	q->nr_sorted--; 	q->end_sector = rq_end_sector(rq);	q->boundary_rq = rq;	list_add_tail(&rq->queuelist, &q->queue_head);} EXPORT_SYMBOL(elv_dispatch_add_tail); int elv_merge(request_queue_t *q, struct request **req, struct bio *bio){	elevator_t *e = q->elevator;	struct request *__rq;	int ret; 	/*	 * First try one-hit cache.	 */	if (q->last_merge) {		ret = elv_try_merge(q->last_merge, bio);		if (ret != ELEVATOR_NO_MERGE) {			*req = q->last_merge;			return ret;		}	} 	/*	 * See if our hash lookup can find a potential backmerge.	 */	__rq = elv_rqhash_find(q, bio->bi_sector);	if (__rq && elv_rq_merge_ok(__rq, bio)) {		*req = __rq;		return ELEVATOR_BACK_MERGE;	} 	if (e->ops->elevator_merge_fn)		return e->ops->elevator_merge_fn(q, req, bio); 	return ELEVATOR_NO_MERGE;} void elv_merged_request(request_queue_t *q, struct request *rq, int type){	elevator_t *e = q->elevator; 	if (e->ops->elevator_merged_fn)		e->ops->elevator_merged_fn(q, rq, type); 	if (type == ELEVATOR_BACK_MERGE)		elv_rqhash_reposition(q, rq); 	q->last_merge = rq;}

Lines 1–500 of 1159. Load more