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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 "dm.h"
#include "dm-path-selector.h"
#include <linux/slab.h>
struct ps_internal {
struct path_selector_type pst;
struct list_head list;
long use;
};
#define pst_to_psi(__pst) container_of((__pst), struct ps_internal, pst)
static LIST_HEAD(_path_selectors);
static DECLARE_RWSEM(_ps_lock);
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) {
if ((psi->use == 0) && !try_module_get(psi->pst.module))
psi = NULL;
else
psi->use++;
}
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;
if (--psi->use == 0)
module_put(psi->pst.module);
if (psi->use < 0)
BUG();
out:
up_read(&_ps_lock);
}
static struct ps_internal *_alloc_path_selector(struct path_selector_type *pst)
{
struct ps_internal *psi = kmalloc(sizeof(*psi), GFP_KERNEL);
if (psi) {
memset(psi, 0, sizeof(*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;
}
if (psi->use) {
up_write(&_ps_lock);
return -ETXTBSY;
}
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);
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