linux/drivers/md/dm-cache-policy.c
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   1/*
   2 * Copyright (C) 2012 Red Hat. All rights reserved.
   3 *
   4 * This file is released under the GPL.
   5 */
   6
   7#include "dm-cache-policy-internal.h"
   8#include "dm.h"
   9
  10#include <linux/module.h>
  11#include <linux/slab.h>
  12
  13/*----------------------------------------------------------------*/
  14
  15#define DM_MSG_PREFIX "cache-policy"
  16
  17static DEFINE_SPINLOCK(register_lock);
  18static LIST_HEAD(register_list);
  19
  20static struct dm_cache_policy_type *__find_policy(const char *name)
  21{
  22        struct dm_cache_policy_type *t;
  23
  24        list_for_each_entry(t, &register_list, list)
  25                if (!strcmp(t->name, name))
  26                        return t;
  27
  28        return NULL;
  29}
  30
  31static struct dm_cache_policy_type *__get_policy_once(const char *name)
  32{
  33        struct dm_cache_policy_type *t = __find_policy(name);
  34
  35        if (t && !try_module_get(t->owner)) {
  36                DMWARN("couldn't get module %s", name);
  37                t = ERR_PTR(-EINVAL);
  38        }
  39
  40        return t;
  41}
  42
  43static struct dm_cache_policy_type *get_policy_once(const char *name)
  44{
  45        struct dm_cache_policy_type *t;
  46
  47        spin_lock(&register_lock);
  48        t = __get_policy_once(name);
  49        spin_unlock(&register_lock);
  50
  51        return t;
  52}
  53
  54static struct dm_cache_policy_type *get_policy(const char *name)
  55{
  56        struct dm_cache_policy_type *t;
  57
  58        t = get_policy_once(name);
  59        if (IS_ERR(t))
  60                return NULL;
  61
  62        if (t)
  63                return t;
  64
  65        request_module("dm-cache-%s", name);
  66
  67        t = get_policy_once(name);
  68        if (IS_ERR(t))
  69                return NULL;
  70
  71        return t;
  72}
  73
  74static void put_policy(struct dm_cache_policy_type *t)
  75{
  76        module_put(t->owner);
  77}
  78
  79int dm_cache_policy_register(struct dm_cache_policy_type *type)
  80{
  81        int r;
  82
  83        /* One size fits all for now */
  84        if (type->hint_size != 0 && type->hint_size != 4) {
  85                DMWARN("hint size must be 0 or 4 but %llu supplied.", (unsigned long long) type->hint_size);
  86                return -EINVAL;
  87        }
  88
  89        spin_lock(&register_lock);
  90        if (__find_policy(type->name)) {
  91                DMWARN("attempt to register policy under duplicate name %s", type->name);
  92                r = -EINVAL;
  93        } else {
  94                list_add(&type->list, &register_list);
  95                r = 0;
  96        }
  97        spin_unlock(&register_lock);
  98
  99        return r;
 100}
 101EXPORT_SYMBOL_GPL(dm_cache_policy_register);
 102
 103void dm_cache_policy_unregister(struct dm_cache_policy_type *type)
 104{
 105        spin_lock(&register_lock);
 106        list_del_init(&type->list);
 107        spin_unlock(&register_lock);
 108}
 109EXPORT_SYMBOL_GPL(dm_cache_policy_unregister);
 110
 111struct dm_cache_policy *dm_cache_policy_create(const char *name,
 112                                               dm_cblock_t cache_size,
 113                                               sector_t origin_size,
 114                                               sector_t cache_block_size)
 115{
 116        struct dm_cache_policy *p = NULL;
 117        struct dm_cache_policy_type *type;
 118
 119        type = get_policy(name);
 120        if (!type) {
 121                DMWARN("unknown policy type");
 122                return NULL;
 123        }
 124
 125        p = type->create(cache_size, origin_size, cache_block_size);
 126        if (!p) {
 127                put_policy(type);
 128                return NULL;
 129        }
 130        p->private = type;
 131
 132        return p;
 133}
 134EXPORT_SYMBOL_GPL(dm_cache_policy_create);
 135
 136void dm_cache_policy_destroy(struct dm_cache_policy *p)
 137{
 138        struct dm_cache_policy_type *t = p->private;
 139
 140        p->destroy(p);
 141        put_policy(t);
 142}
 143EXPORT_SYMBOL_GPL(dm_cache_policy_destroy);
 144
 145const char *dm_cache_policy_get_name(struct dm_cache_policy *p)
 146{
 147        struct dm_cache_policy_type *t = p->private;
 148
 149        return t->name;
 150}
 151EXPORT_SYMBOL_GPL(dm_cache_policy_get_name);
 152
 153const unsigned *dm_cache_policy_get_version(struct dm_cache_policy *p)
 154{
 155        struct dm_cache_policy_type *t = p->private;
 156
 157        return t->version;
 158}
 159EXPORT_SYMBOL_GPL(dm_cache_policy_get_version);
 160
 161size_t dm_cache_policy_get_hint_size(struct dm_cache_policy *p)
 162{
 163        struct dm_cache_policy_type *t = p->private;
 164
 165        return t->hint_size;
 166}
 167EXPORT_SYMBOL_GPL(dm_cache_policy_get_hint_size);
 168
 169/*----------------------------------------------------------------*/
 170
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