Release 4.18 block/elevator.c

/*
 *  Block device elevator/IO-scheduler.
 *
 *  Copyright (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE
 *
 * 30042000 Jens Axboe <axboe@kernel.dk> :
 *
 * Split the elevator a bit so that it is possible to choose a different
 * one or even write a new "plug in". There are three pieces:
 * - elevator_fn, inserts a new request in the queue list
 * - elevator_merge_fn, decides whether a new buffer can be merged with
 *   an existing request
 * - elevator_dequeue_fn, called when a request is taken off the active list
 *
 * 20082000 Dave Jones <davej@suse.de> :
 * Removed tests for max-bomb-segments, which was breaking elvtune
 *  when run without -bN
 *
 * Jens:
 * - Rework again to work with bio instead of buffer_heads
 * - loose bi_dev comparisons, partition handling is right now
 * - completely modularize elevator setup and teardown
 *
 */
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/blkdev.h>
#include <linux/elevator.h>
#include <linux/bio.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/compiler.h>
#include <linux/blktrace_api.h>
#include <linux/hash.h>
#include <linux/uaccess.h>
#include <linux/pm_runtime.h>
#include <linux/blk-cgroup.h>

#include <trace/events/block.h>

#include "blk.h"
#include "blk-mq-sched.h"
#include "blk-wbt.h"

static DEFINE_SPINLOCK(elv_list_lock);
static LIST_HEAD(elv_list);

/*
 * Merge hash stuff.
 */

#define rq_hash_key(rq)		(blk_rq_pos(rq) + blk_rq_sectors(rq))

/*
 * Query io scheduler to see if the current process issuing bio may be
 * merged with rq.
 */


static int elv_iosched_allow_bio_merge(struct request *rq, struct bio *bio)
{
	struct request_queue *q = rq->q;
	struct elevator_queue *e = q->elevator;

	if (e->uses_mq && e->type->ops.mq.allow_merge)
		return e->type->ops.mq.allow_merge(q, rq, bio);
	else if (!e->uses_mq && e->type->ops.sq.elevator_allow_bio_merge_fn)
		return e->type->ops.sq.elevator_allow_bio_merge_fn(q, rq, bio);

	return 1;
}

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3
2.80%
1
14.29%
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107
100.00%
7
100.00%

/*
 * 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;
}
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1
14.29%
Tahsin Erdogan
5
11.36%
1
14.29%
Martin K. Petersen
5
11.36%
1
14.29%
Tejun Heo
3
6.82%
1
14.29%
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44
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EXPORT_SYMBOL(elv_bio_merge_ok);



static bool elevator_match(const struct elevator_type *e, const char *name)
{
	if (!strcmp(e->elevator_name, name))
		return true;
	if (e->elevator_alias && !strcmp(e->elevator_alias, name))
		return true;

	return false;
}

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/*
 * Return scheduler with name 'name' and with matching 'mq capability
 */


static struct elevator_type *elevator_find(const char *name, bool mq)
{
	struct elevator_type *e;

	list_for_each_entry(e, &elv_list, list) {
		if (elevator_match(e, name) && (mq == e->uses_mq))
			return e;
	}

	return NULL;
}

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4
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1
16.67%
Adrian Bunk
1
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54
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static void elevator_put(struct elevator_type *e)
{
	module_put(e->elevator_owner);
}

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static struct elevator_type *elevator_get(struct request_queue *q,
					  const char *name, bool try_loading)
{
	struct elevator_type *e;

	spin_lock(&elv_list_lock);

	e = elevator_find(name, q->mq_ops != NULL);
	if (!e && try_loading) {
		spin_unlock(&elv_list_lock);
		request_module("%s-iosched", name);
		spin_lock(&elv_list_lock);
		e = elevator_find(name, q->mq_ops != NULL);
	}

	if (e && !try_module_get(e->elevator_owner))
		e = NULL;

	spin_unlock(&elv_list_lock);
	return e;
}

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1
0.90%
1
12.50%
Kees Cook
1
0.90%
1
12.50%
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111
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8
100.00%


static char chosen_elevator[ELV_NAME_MAX];



static int __init elevator_setup(char *str)
{
	/*
         * Be backwards-compatible with previous kernels, so users
         * won't get the wrong elevator.
         */
	strncpy(chosen_elevator, str, sizeof(chosen_elevator) - 1);
	return 1;
}

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2
6.90%
1
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Linus Torvalds
2
6.90%
1
14.29%
Hirofumi Ogawa
1
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Chuck Ebbert
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__setup("elevator=", elevator_setup);

/* called during boot to load the elevator chosen by the elevator param */


void __init load_default_elevator_module(void)
{
	struct elevator_type *e;

	if (!chosen_elevator[0])
		return;

	/*
         * Boot parameter is deprecated, we haven't supported that for MQ.
         * Only look for non-mq schedulers from here.
         */
	spin_lock(&elv_list_lock);
	e = elevator_find(chosen_elevator, false);
	spin_unlock(&elv_list_lock);

	if (!e)
		request_module("%s-iosched", chosen_elevator);
}

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static struct kobj_type elv_ktype;



struct elevator_queue *elevator_alloc(struct request_queue *q,
				  struct elevator_type *e)
{
	struct elevator_queue *eq;

	eq = kzalloc_node(sizeof(*eq), GFP_KERNEL, q->node);
	if (unlikely(!eq))
		return NULL;

	eq->type = e;
	kobject_init(&eq->kobj, &elv_ktype);
	mutex_init(&eq->sysfs_lock);
	hash_init(eq->hash);
	eq->uses_mq = e->uses_mq;

	return eq;
}
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43.01%
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38.46%
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3
3.23%
3
23.08%
Chao Yu
3
3.23%
1
7.69%
Joe Perches
1
1.08%
1
7.69%
Sasha Levin
1
1.08%
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Tejun Heo
1
1.08%
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EXPORT_SYMBOL(elevator_alloc);



static void elevator_release(struct kobject *kobj)
{
	struct elevator_queue *e;

	e = container_of(kobj, struct elevator_queue, kobj);
	elevator_put(e->type);
	kfree(e);
}

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2.50%
1
33.33%
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40
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3
100.00%

/*
 * Use the default elevator specified by config boot param for non-mq devices,
 * or by config option.  Don't try to load modules as we could be running off
 * async and request_module() isn't allowed from async.
 */


int elevator_init(struct request_queue *q)
{
	struct elevator_type *e = NULL;
	int err = 0;

	/*
         * q->sysfs_lock must be held to provide mutual exclusion between
         * elevator_switch() and here.
         */
	mutex_lock(&q->sysfs_lock);
	if (unlikely(q->elevator))
		goto out_unlock;

	if (*chosen_elevator) {
		e = elevator_get(q, chosen_elevator, false);
		if (!e)
			printk(KERN_ERR "I/O scheduler %s not found\n",
							chosen_elevator);
	}

	if (!e)
		e = elevator_get(q, CONFIG_DEFAULT_IOSCHED, false);
	if (!e) {
		printk(KERN_ERR
			"Default I/O scheduler not found. Using noop.\n");
		e = elevator_get(q, "noop", false);
	}

	err = e->ops.sq.elevator_init_fn(q, e);
	if (err)
		elevator_put(e);
out_unlock:
	mutex_unlock(&q->sysfs_lock);
	return err;
}

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17
11.26%
2
10.00%
Tejun Heo
14
9.27%
3
15.00%
Linus Torvalds
10
6.62%
1
5.00%
Sudip Mukherjee
10
6.62%
1
5.00%
Mike Snitzer
9
5.96%
1
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Tomoki Sekiyama
8
5.30%
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Jianpeng Ma (马建朋)
2
1.32%
1
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151
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void elevator_exit(struct request_queue *q, struct elevator_queue *e)
{
	mutex_lock(&e->sysfs_lock);
	if (e->uses_mq && e->type->ops.mq.exit_sched)
		blk_mq_exit_sched(q, e);
	else if (!e->uses_mq && e->type->ops.sq.elevator_exit_fn)
		e->type->ops.sq.elevator_exit_fn(e);
	mutex_unlock(&e->sysfs_lock);

	kobject_put(&e->kobj);
}

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8
8.60%
1
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Tejun Heo
6
6.45%
1
14.29%
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93
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7
100.00%



static inline void __elv_rqhash_del(struct request *rq)
{
	hash_del(&rq->hash);
	rq->rq_flags &= ~RQF_HASHED;
}

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void elv_rqhash_del(struct request_queue *q, struct request *rq)
{
	if (ELV_ON_HASH(rq))
		__elv_rqhash_del(rq);
}
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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;
}
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2
3.64%
1
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55
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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);
}

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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;
}

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100.00%
4
100.00%

/*
 * 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);
}
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2
1.55%
1
33.33%
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129
100.00%
3
100.00%

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);
}
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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;
}
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EXPORT_SYMBOL(elv_rb_find);

/*
 * Insert rq into dispatch queue of q.  Queue lock must be held on
 * entry.  rq is sort instead into the dispatch queue. To be used by
 * specific elevators.
 */


void elv_dispatch_sort(struct request_queue *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 (req_op(rq) != req_op(pos))
			break;
		if (rq_data_dir(rq) != rq_data_dir(pos))
			break;
		if (pos->rq_flags & (RQF_STARTED | RQF_SOFTBARRIER))
			break;
		if (blk_rq_pos(rq) >= boundary) {
			if (blk_rq_pos(pos) < boundary)
				continue;
		} else {
			if (blk_rq_pos(pos) >= boundary)
				break;
		}
		if (blk_rq_pos(rq) >= blk_rq_pos(pos))
			break;
	}

	list_add(&rq->queuelist, entry);
}
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4.14%
1
9.09%
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6
3.55%
1
9.09%
Michael Christie
6
3.55%
1
9.09%
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169
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11
100.00%

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);
}
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EXPORT_SYMBOL(elv_dispatch_add_tail);



enum elv_merge elv_merge(struct request_queue *q, struct request **req,
		struct bio *bio)
{
	struct elevator_queue *e = q->elevator;
	struct request *__rq;

	/*
         * Levels of merges:
         *      nomerges:  No merges at all attempted
         *      noxmerges: Only simple one-hit cache try
         *      merges:    All merge tries attempted
         */
	if (blk_queue_nomerges(q) || !bio_mergeable(bio))
		return ELEVATOR_NO_MERGE;

	/*
         * First try one-hit cache.
         */
	if (q->last_merge && elv_bio_merge_ok(q->last_merge, bio)) {
		enum elv_merge ret = blk_try_merge(q->last_merge, bio);

		if (ret != ELEVATOR_NO_MERGE) {
			*req = q->last_merge;
			return ret;
		}
	}

	if (blk_queue_noxmerges(q))
		return ELEVATOR_NO_MERGE;

	/*
         * See if our hash lookup can find a potential backmerge.
         */
	__rq = elv_rqhash_find(q, bio->bi_iter.bi_sector);
	if (__rq && elv_bio_merge_ok(__rq, bio)) {
		*req = __rq;
		return ELEVATOR_BACK_MERGE;
	}

	if (e->uses_mq && e->type->ops.mq.request_merge)
		return e->type->ops.mq.request_merge(q, req, bio);
	else if (!e->uses_mq && e->type->ops.sq.elevator_merge_fn)
		return e->type->ops.sq.elevator_merge_fn(q, req, bio);

	return ELEVATOR_NO_MERGE;
}

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21
9.55%
2
11.76%
Linus Torvalds
20
9.09%
1
5.88%
Ming Lei
6
2.73%
1
5.88%
Christoph Hellwig
6
2.73%
1
5.88%
Kent Overstreet
2
0.91%
1
5.88%
Tahsin Erdogan
2
0.91%
1
5.88%
Total
220
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17
100.00%

/*
 * Attempt to do an insertion back merge. Only check for the case where
 * we can append 'rq' to an existing request, so we can throw 'rq' away
 * afterwards.
 *
 * Returns true if we merged, false otherwise
 */


bool elv_attempt_insert_merge(struct request_queue *q, struct request *rq)
{
	struct request *__rq;
	bool ret;

	if (blk_queue_nomerges(q))
		return false;

	/*
         * First try one-hit cache.
         */
	if (q->last_merge && blk_attempt_req_merge(q, q->last_merge, rq))
		return true;

	if (blk_queue_noxmerges(q))
		return false;

	ret = false;
	/*
         * See if our hash lookup can find a potential backmerge.
         */
	while (1) {
		__rq = elv_rqhash_find(q, blk_rq_pos(rq));
		if (!__rq || !blk_attempt_req_merge(q, __rq, rq))
			break;

		/* The merged request could be merged with others, try again */
		ret = true;
		rq = __rq;
	}

	return ret;
}

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100.00%
2
100.00%



void elv_merged_request(struct request_queue *q, struct request *rq,
		enum elv_merge type)
{
	struct elevator_queue *e = q->elevator;

	if (e->uses_mq && e->type->ops.mq.request_merged)
		e->type->ops.mq.request_merged(q, rq, type);
	else if (!e->uses_mq && e->type->ops.sq.elevator_merged_fn)
		e->type->ops.sq.elevator_merged_fn(q, rq, type);

	if (type == ELEVATOR_BACK_MERGE)
		elv_rqhash_reposition(q, rq);

	q->last_merge = rq;
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
Jens Axboe
101
87.83%
8
72.73%
Tejun Heo
12
10.43%
2
18.18%
Christoph Hellwig
2
1.74%
1
9.09%
Total
115
100.00%
11
100.00%



void elv_merge_requests(struct request_queue *q, struct request *rq,
			     struct request *next)
{
	struct elevator_queue *e = q->elevator;
	bool next_sorted = false;

	if (e->uses_mq && e->type->ops.mq.requests_merged)
		e->type->ops.mq.requests_merged(q, rq, next);
	else if (e->type->ops.sq.elevator_merge_req_fn) {
		next_sorted = (__force bool)(next->rq_flags & RQF_SORTED);
		if (next_sorted)
			e->type->ops.sq.elevator_merge_req_fn(q, rq, next);
	}

	elv_rqhash_reposition(q, rq);

	if (next_sorted) {
		elv_rqhash_del(q, next);
		q->nr_sorted--;
	}

	q->last_merge = rq;
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
Jens Axboe
87
58.78%
8
61.54%
Linus Torvalds
38
25.68%
1
7.69%
Tejun Heo
17
11.49%
3
23.08%
Bart Van Assche
6
4.05%
1
7.69%
Total
148
100.00%
13
100.00%



void elv_bio_merged(struct request_queue *q, struct request *rq,
			struct bio *bio)
{
	struct elevator_queue *e = q->elevator;

	if (WARN_ON_ONCE(e->uses_mq))
		return;

	if (e->type->ops.sq.elevator_bio_merged_fn)
		e->type->ops.sq.elevator_bio_merged_fn(q, rq, bio);
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
Divyesh Shah
48
70.59%
1
25.00%
Jens Axboe
14
20.59%
2
50.00%
Tejun Heo
6
8.82%
1
25.00%
Total
68
100.00%
4
100.00%

#ifdef CONFIG_PM


static void blk_pm_requeue_request(struct request *rq)
{
	if (rq->q->dev && !(rq->rq_flags & RQF_PM))
		rq->q->nr_pending--;
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
Lin Ming
33
94.29%
1
50.00%
Christoph Hellwig
2
5.71%
1
50.00%
Total
35
100.00%
2
100.00%



static void blk_pm_add_request(struct request_queue *q, struct request *rq)
{
	if (q->dev && !(rq->rq_flags & RQF_PM) && q->nr_pending++ == 0 &&
	    (q->rpm_status == RPM_SUSPENDED || q->rpm_status == RPM_SUSPENDING))
		pm_request_resume(q->dev);
}
Contributors
Person
Tokens
Prop
Commits
CommitProp
Lin Ming
57
96.61%
1
50.00%
Christoph Hellwig
2
3.39%
1
50.00%
Total
59
100.00%
2
100.00%

#else


static inline void blk_pm_requeue_request(struct request *rq) {}
Contributors
Person
Tokens
Prop
Commits
CommitProp
Lin Ming
11
100.00%
1
100.00%
Total
11
100.00%
1
100.00%



static inline void blk_pm_add_request(struct request_queue *q,
				      struct request *rq)
{
}
Contributors
Person
Tokens
Prop
Commits
CommitProp
Lin Ming
16
100.00%
1
100.00%
Total
16
100.00%
1
100.00%

#endif



void elv_requeue_request(struct request_queue *q, struct request *rq)
{
	/*
         * it already went through dequeue, we need to decrement the
         * in_flight count again
         */
	if (blk_account_rq(rq)) {
		q->in_flight[rq_is_sync(rq)]--;
		if (rq->rq_flags & RQF_SORTED)
			elv_deactivate_rq(q, rq);
	}

	rq->rq_flags &= ~RQF_STARTED;

	blk_pm_requeue_request(rq);

	__elv_add_request(q, rq, ELEVATOR_INSERT_REQUEUE);
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
Jens Axboe
41
56.94%
6
50.00%
Andrew Morton
13
18.06%
1
8.33%
Tejun Heo
7
9.72%
2
16.67%
Christoph Hellwig
6
8.33%
2
16.67%
Lin Ming
5
6.94%
1
8.33%
Total
72
100.00%
12
100.00%



void elv_drain_elevator(struct request_queue *q)
{
	struct elevator_queue *e = q->elevator;
	static int printed;

	if (WARN_ON_ONCE(e->uses_mq))
		return;

	lockdep_assert_held(q->queue_lock);

	while (e->type->ops.sq.elevator_dispatch_fn(q, 1))
		;
	if (q->nr_sorted && printed++ < 10) {
		printk(KERN_ERR "%s: forced dispatching is broken "
		       "(nr_sorted=%u), please report this\n",
		       q->elevator->type->elevator_name, q->nr_sorted);
	}
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
Tejun Heo
66
73.33%
3
50.00%
Jens Axboe
24
26.67%
3
50.00%
Total
90
100.00%
6
100.00%



void __elv_add_request(struct request_queue *q, struct request *rq, int where)
{
	trace_block_rq_insert(q, rq);

	blk_pm_add_request(q, rq);

	rq->q = q;

	if (rq->rq_flags & RQF_SOFTBARRIER) {
		/* barriers are scheduling boundary, update end_sector */
		if (!blk_rq_is_passthrough(rq)) {
			q->end_sector = rq_end_sector(rq);
			q