// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2012 Red Hat. All rights reserved.
 *
 * This file is released under the GPL.
 */

#include "dm-cache-policy-internal.h"
#include "dm.h"

#include <linux/module.h>
#include <linux/slab.h>

/*----------------------------------------------------------------*/

#define DM_MSG_PREFIX "cache-policy"

static DEFINE_SPINLOCK(register_lock);
static LIST_HEAD(register_list);

static struct dm_cache_policy_type *__find_policy(const char *name)
{
        struct dm_cache_policy_type *t;

        list_for_each_entry(t, &register_list, list)
                if (!strcmp(t->name, name))
                        return t;

        return NULL;
}

static struct dm_cache_policy_type *__get_policy_once(const char *name)
{
        struct dm_cache_policy_type *t = __find_policy(name);

        if (t && !try_module_get(t->owner)) {
                DMWARN("couldn't get module %s", name);
                t = ERR_PTR(-EINVAL);
        }

        return t;
}

static struct dm_cache_policy_type *get_policy_once(const char *name)
{
        struct dm_cache_policy_type *t;

        spin_lock(&register_lock);
        t = __get_policy_once(name);
        spin_unlock(&register_lock);

        return t;
}

static struct dm_cache_policy_type *get_policy(const char *name)
{
        struct dm_cache_policy_type *t;

        t = get_policy_once(name);
        if (IS_ERR(t))
                return NULL;

        if (t)
                return t;

        request_module("dm-cache-%s", name);

        t = get_policy_once(name);
        if (IS_ERR(t))
                return NULL;

        return t;
}

static void put_policy(struct dm_cache_policy_type *t)
{
        module_put(t->owner);
}

int dm_cache_policy_register(struct dm_cache_policy_type *type)
{
        int r;

        /* One size fits all for now */
        if (type->hint_size != 0 && type->hint_size != 4) {
                DMWARN("hint size must be 0 or 4 but %llu supplied.", (unsigned long long) type->hint_size);
                return -EINVAL;
        }

        spin_lock(&register_lock);
        if (__find_policy(type->name)) {
                DMWARN("attempt to register policy under duplicate name %s", type->name);
                r = -EINVAL;
        } else {
                list_add(&type->list, &register_list);
                r = 0;
        }
        spin_unlock(&register_lock);

        return r;
}
EXPORT_SYMBOL_GPL(dm_cache_policy_register);

void dm_cache_policy_unregister(struct dm_cache_policy_type *type)
{
        spin_lock(&register_lock);
        list_del_init(&type->list);
        spin_unlock(&register_lock);
}
EXPORT_SYMBOL_GPL(dm_cache_policy_unregister);

struct dm_cache_policy *dm_cache_policy_create(const char *name,
                                               dm_cblock_t cache_size,
                                               sector_t origin_size,
                                               sector_t cache_block_size)
{
        struct dm_cache_policy *p = NULL;
        struct dm_cache_policy_type *type;

        type = get_policy(name);
        if (!type) {
                DMWARN("unknown policy type");
                return ERR_PTR(-EINVAL);
        }

        p = type->create(cache_size, origin_size, cache_block_size);
        if (!p) {
                put_policy(type);
                return ERR_PTR(-ENOMEM);
        }
        p->private = type;

        return p;
}
EXPORT_SYMBOL_GPL(dm_cache_policy_create);

void dm_cache_policy_destroy(struct dm_cache_policy *p)
{
        struct dm_cache_policy_type *t = p->private;

        p->destroy(p);
        put_policy(t);
}
EXPORT_SYMBOL_GPL(dm_cache_policy_destroy);

const char *dm_cache_policy_get_name(struct dm_cache_policy *p)
{
        struct dm_cache_policy_type *t = p->private;

        /* if t->real is set then an alias was used (e.g. "default") */
        if (t->real)
                return t->real->name;

        return t->name;
}
EXPORT_SYMBOL_GPL(dm_cache_policy_get_name);

const unsigned int *dm_cache_policy_get_version(struct dm_cache_policy *p)
{
        struct dm_cache_policy_type *t = p->private;

        return t->version;
}
EXPORT_SYMBOL_GPL(dm_cache_policy_get_version);

size_t dm_cache_policy_get_hint_size(struct dm_cache_policy *p)
{
        struct dm_cache_policy_type *t = p->private;

        return t->hint_size;
}
EXPORT_SYMBOL_GPL(dm_cache_policy_get_hint_size);

/*----------------------------------------------------------------*/