dm-path-selector.c

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/*
 * Copyright (C) 2003 Sistina Software.
 * Copyright (C) 2004 Red Hat, Inc. All rights reserved.
 *
 * Module Author: Heinz Mauelshagen
 *
 * This file is released under the GPL.
 *
 * Path selector registration.
 */

#include <linux/device-mapper.h>
#include <linux/module.h>

#include "dm-path-selector.h"

#include <linux/slab.h>

struct ps_internal {
    struct path_selector_type pst;
    struct list_head list;
};

#define pst_to_psi(__pst) container_of((__pst), struct ps_internal, pst)

static LIST_HEAD(_path_selectors);
static DECLARE_RWSEM(_ps_lock);

static struct ps_internal *__find_path_selector_type(const char *name)
{
    struct ps_internal *psi;

    list_for_each_entry(psi, &_path_selectors, list) {
        if (!strcmp(name, psi->pst.name))
            return psi;
    }

    return NULL;
}

static struct ps_internal *get_path_selector(const char *name)
{
    struct ps_internal *psi;

    down_read(&_ps_lock);
    psi = __find_path_selector_type(name);
    if (psi && !try_module_get(psi->pst.module))
        psi = NULL;
    up_read(&_ps_lock);

    return psi;
}

struct path_selector_type *dm_get_path_selector(const char *name)
{
    struct ps_internal *psi;

    if (!name)
        return NULL;

    psi = get_path_selector(name);
    if (!psi) {
        request_module("dm-%s", name);
        psi = get_path_selector(name);
    }

    return psi ? &psi->pst : NULL;
}

void dm_put_path_selector(struct path_selector_type *pst)
{
    struct ps_internal *psi;

    if (!pst)
        return;

    down_read(&_ps_lock);
    psi = __find_path_selector_type(pst->name);
    if (!psi)
        goto out;

    module_put(psi->pst.module);
out:
    up_read(&_ps_lock);
}

static struct ps_internal *_alloc_path_selector(struct path_selector_type *pst)
{
    struct ps_internal *psi = kzalloc(sizeof(*psi), GFP_KERNEL);

    if (psi)
        psi->pst = *pst;

    return psi;
}

int dm_register_path_selector(struct path_selector_type *pst)
{
    int r = 0;
    struct ps_internal *psi = _alloc_path_selector(pst);

    if (!psi)
        return -ENOMEM;

    down_write(&_ps_lock);

    if (__find_path_selector_type(pst->name)) {
        kfree(psi);
        r = -EEXIST;
    } else
        list_add(&psi->list, &_path_selectors);

    up_write(&_ps_lock);

    return r;
}

int dm_unregister_path_selector(struct path_selector_type *pst)
{
    struct ps_internal *psi;

    down_write(&_ps_lock);

    psi = __find_path_selector_type(pst->name);
    if (!psi) {
        up_write(&_ps_lock);
        return -EINVAL;
    }

    list_del(&psi->list);

    up_write(&_ps_lock);

    kfree(psi);

    return 0;
}

EXPORT_SYMBOL_GPL(dm_register_path_selector);
EXPORT_SYMBOL_GPL(dm_unregister_path_selector);