linux-imx

/*

 *  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-pm.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->type->ops.allow_merge)

        return e->type->ops.allow_merge(q, rq, bio);

​

    return 1;

}

​

/*

 * 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);

​

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;