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// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (C) 2001 Sistina Software (UK) Limited
*
* This file is released under the GPL.
*/
#include "dm-core.h"
#include <linux/module.h>
#include <linux/init.h>
#include <linux/kmod.h>
#include <linux/bio.h>
#include <linux/dax.h>
#define DM_MSG_PREFIX "target"
static LIST_HEAD(_targets);
static DECLARE_RWSEM(_lock);
static inline struct target_type *__find_target_type(const char *name)
{
struct target_type *tt;
list_for_each_entry(tt, &_targets, list)
if (!strcmp(name, tt->name))
return tt;
return NULL;
}
static struct target_type *get_target_type(const char *name)
{
struct target_type *tt;
down_read(&_lock);
tt = __find_target_type(name);
if (tt && !try_module_get(tt->module))
tt = NULL;
up_read(&_lock);
return tt;
}
static void load_module(const char *name)
{
request_module("dm-%s", name);
}
struct target_type *dm_get_target_type(const char *name)
{
struct target_type *tt = get_target_type(name);
if (!tt) {
load_module(name);
tt = get_target_type(name);
}
return tt;
}
void dm_put_target_type(struct target_type *tt)
{
down_read(&_lock);
module_put(tt->module);
up_read(&_lock);
}
int dm_target_iterate(void (*iter_func)(struct target_type *tt,
void *param), void *param)
{
struct target_type *tt;
down_read(&_lock);
list_for_each_entry(tt, &_targets, list)
iter_func(tt, param);
up_read(&_lock);
return 0;
}
int dm_register_target(struct target_type *tt)
{
int rv = 0;
down_write(&_lock);
if (__find_target_type(tt->name))
rv = -EEXIST;
else
list_add(&tt->list, &_targets);
up_write(&_lock);
return rv;
}
void dm_unregister_target(struct target_type *tt)
{
down_write(&_lock);
if (!__find_target_type(tt->name)) {
DMCRIT("Unregistering unrecognised target: %s", tt->name);
BUG();
}
list_del(&tt->list);
up_write(&_lock);
}
/*
* io-err: always fails an io, useful for bringing
* up LVs that have holes in them.
*/
static int io_err_ctr(struct dm_target *tt, unsigned int argc, char **args)
{
/*
* Return error for discards instead of -EOPNOTSUPP
*/
tt->num_discard_bios = 1;
return 0;
}
static void io_err_dtr(struct dm_target *tt)
{
/* empty */
}
static int io_err_map(struct dm_target *tt, struct bio *bio)
{
return DM_MAPIO_KILL;
}
static int io_err_clone_and_map_rq(struct dm_target *ti, struct request *rq,
union map_info *map_context,
struct request **clone)
{
return DM_MAPIO_KILL;
}
static void io_err_release_clone_rq(struct request *clone,
union map_info *map_context)
{
}
static long io_err_dax_direct_access(struct dm_target *ti, pgoff_t pgoff,
long nr_pages, enum dax_access_mode mode, void **kaddr,
pfn_t *pfn)
{
return -EIO;
}
static struct target_type error_target = {
.name = "error",
.version = {1, 5, 0},
.features = DM_TARGET_WILDCARD,
.ctr = io_err_ctr,
.dtr = io_err_dtr,
.map = io_err_map,
.clone_and_map_rq = io_err_clone_and_map_rq,
.release_clone_rq = io_err_release_clone_rq,
.direct_access = io_err_dax_direct_access,
};
int __init dm_target_init(void)
{
return dm_register_target(&error_target);
}
void dm_target_exit(void)
{
dm_unregister_target(&error_target);
}
EXPORT_SYMBOL(dm_register_target);
EXPORT_SYMBOL(dm_unregister_target);
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