linux-imx

/*

 * Copyright (C) 2004-2005 IBM Corp.  All Rights Reserved.

 * Copyright (C) 2006-2009 NEC Corporation.

 *

 * dm-queue-length.c

 *

 * Module Author: Stefan Bader, IBM

 * Modified by: Kiyoshi Ueda, NEC

 *

 * This file is released under the GPL.

 *

 * queue-length path selector - choose a path with the least number of

 * in-flight I/Os.

 */

​

#include "dm.h"

#include "dm-path-selector.h"

​

#include <linux/slab.h>

#include <linux/ctype.h>

#include <linux/errno.h>

#include <linux/module.h>

#include <linux/atomic.h>

​

#define DM_MSG_PREFIX   "multipath queue-length"

#define QL_MIN_IO   1

#define QL_VERSION  "0.2.0"

​

struct selector {

    struct list_head    valid_paths;

    struct list_head    failed_paths;

    spinlock_t lock;

};

​

struct path_info {

    struct list_head    list;

    struct dm_path      *path;

    unsigned        repeat_count;

    atomic_t        qlen;   /* the number of in-flight I/Os */

};

​

static struct selector *alloc_selector(void)

{

    struct selector *s = kmalloc(sizeof(*s), GFP_KERNEL);

​

    if (s) {

        INIT_LIST_HEAD(&s->valid_paths);

        INIT_LIST_HEAD(&s->failed_paths);

        spin_lock_init(&s->lock);

    }

​

    return s;

}

​

static int ql_create(struct path_selector *ps, unsigned argc, char **argv)

{

    struct selector *s = alloc_selector();

​

    if (!s)

        return -ENOMEM;

​

    ps->context = s;

    return 0;

}

​

static void ql_free_paths(struct list_head *paths)

{

    struct path_info *pi, *next;

​

    list_for_each_entry_safe(pi, next, paths, list) {

        list_del(&pi->list);

        kfree(pi);

    }

}

​

static void ql_destroy(struct path_selector *ps)

{

    struct selector *s = ps->context;

​

    ql_free_paths(&s->valid_paths);

    ql_free_paths(&s->failed_paths);

    kfree(s);

    ps->context = NULL;

}

​

static int ql_status(struct path_selector *ps, struct dm_path *path,

             status_type_t type, char *result, unsigned maxlen)

{

    unsigned sz = 0;

    struct path_info *pi;

​

    /* When called with NULL path, return selector status/args. */