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/*
* Copyright (C) 2001 Sistina Software (UK) Limited
*
* This file is released under the GPL.
*/
#include "dm.h"
#include <linux/module.h>
#include <linux/init.h>
#include <linux/kmod.h>
#include <linux/bio.h>
#include <linux/slab.h>
struct tt_internal {
struct target_type tt;
struct list_head list;
long use;
};
static LIST_HEAD(_targets);
static DECLARE_RWSEM(_lock);
#define DM_MOD_NAME_SIZE 32
static inline struct tt_internal *__find_target_type(const char *name)
{
struct tt_internal *ti;
list_for_each_entry (ti, &_targets, list)
if (!strcmp(name, ti->tt.name))
return ti;
return NULL;
}
static struct tt_internal *get_target_type(const char *name)
{
struct tt_internal *ti;
down_read(&_lock);
ti = __find_target_type(name);
if (ti) {
if ((ti->use == 0) && !try_module_get(ti->tt.module))
ti = NULL;
else
ti->use++;
}
up_read(&_lock);
return ti;
}
static void load_module(const char *name)
{
request_module("dm-%s", name);
}
struct target_type *dm_get_target_type(const char *name)
{
struct tt_internal *ti = get_target_type(name);
if (!ti) {
load_module(name);
ti = get_target_type(name);
}
return ti ? &ti->tt : NULL;
}
void dm_put_target_type(struct target_type *t)
{
struct tt_internal *ti = (struct tt_internal *) t;
down_read(&_lock);
if (--ti->use == 0)
module_put(ti->tt.module);
if (ti->use < 0)
BUG();
up_read(&_lock);
return;
}
static struct tt_internal *alloc_target(struct target_type *t)
{
struct tt_internal *ti = kmalloc(sizeof(*ti), GFP_KERNEL);
if (ti) {
memset(ti, 0, sizeof(*ti));
ti->tt = *t;
}
return ti;
}
int dm_target_iterate(void (*iter_func)(struct target_type *tt,
void *param), void *param)
{
struct tt_internal *ti;
down_read(&_lock);
list_for_each_entry (ti, &_targets, list)
iter_func(&ti->tt, param);
up_read(&_lock);
return 0;
}
int dm_register_target(struct target_type *t)
{
int rv = 0;
struct tt_internal *ti = alloc_target(t);
if (!ti)
return -ENOMEM;
down_write(&_lock);
if (__find_target_type(t->name))
rv = -EEXIST;
else
list_add(&ti->list, &_targets);
up_write(&_lock);
if (rv)
kfree(ti);
return rv;
}
int dm_unregister_target(struct target_type *t)
{
struct tt_internal *ti;
down_write(&_lock);
if (!(ti = __find_target_type(t->name))) {
up_write(&_lock);
return -EINVAL;
}
if (ti->use) {
up_write(&_lock);
return -ETXTBSY;
}
list_del(&ti->list);
kfree(ti);
up_write(&_lock);
return 0;
}
/*
* io-err: always fails an io, useful for bringing
* up LVs that have holes in them.
*/
static int io_err_ctr(struct dm_target *ti, unsigned int argc, char **args)
{
return 0;
}
static void io_err_dtr(struct dm_target *ti)
{
/* empty */
}
static int io_err_map(struct dm_target *ti, struct bio *bio,
union map_info *map_context)
{
return -EIO;
}
static struct target_type error_target = {
.name = "error",
.version = {1, 0, 1},
.ctr = io_err_ctr,
.dtr = io_err_dtr,
.map = io_err_map,
};
int __init dm_target_init(void)
{
return dm_register_target(&error_target);
}
void dm_target_exit(void)
{
if (dm_unregister_target(&error_target))
DMWARN("error target unregistration failed");
}
EXPORT_SYMBOL(dm_register_target);
EXPORT_SYMBOL(dm_unregister_target);
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