[deliverable/linux.git] / drivers / md / dm-path-selector.c

/*
 * 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 <linux/device-mapper.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);

static 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);

	BUG_ON(psi->use < 0);

out:
	up_read(&_ps_lock);
}

static struct ps_internal *_alloc_path_selector(struct path_selector_type *pst)
{
	struct ps_internal *psi = kzalloc(sizeof(*psi), GFP_KERNEL);

	if (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);
Commit	Line	Data
1da177e4 LT	1	/*
	2	* Copyright (C) 2003 Sistina Software.
	3	* Copyright (C) 2004 Red Hat, Inc. All rights reserved.
	4	*
	5	* Module Author: Heinz Mauelshagen
	6	*
	7	* This file is released under the GPL.
	8	*
	9	* Path selector registration.
	10	*/
	11
586e80e6 MP	12	#include <linux/device-mapper.h>
586e80e6 MP	13
1da177e4 LT	14	#include "dm-path-selector.h"
	15
	16	#include <linux/slab.h>
	17
	18	struct ps_internal {
	19	struct path_selector_type pst;
	20
	21	struct list_head list;
	22	long use;
	23	};
	24
	25	#define pst_to_psi(__pst) container_of((__pst), struct ps_internal, pst)
	26
	27	static LIST_HEAD(_path_selectors);
	28	static DECLARE_RWSEM(_ps_lock);
	29
5e198d94	30	static struct ps_internal __find_path_selector_type(const char name)
1da177e4 LT	31	{
	32	struct ps_internal *psi;
	33
	34	list_for_each_entry(psi, &_path_selectors, list) {
	35	if (!strcmp(name, psi->pst.name))
	36	return psi;
	37	}
	38
	39	return NULL;
	40	}
	41
	42	static struct ps_internal get_path_selector(const char name)
	43	{
	44	struct ps_internal *psi;
	45
	46	down_read(&_ps_lock);
	47	psi = __find_path_selector_type(name);
	48	if (psi) {
	49	if ((psi->use == 0) && !try_module_get(psi->pst.module))
	50	psi = NULL;
	51	else
	52	psi->use++;
	53	}
	54	up_read(&_ps_lock);
	55
	56	return psi;
	57	}
	58
	59	struct path_selector_type dm_get_path_selector(const char name)
	60	{
	61	struct ps_internal *psi;
	62
	63	if (!name)
	64	return NULL;
	65
	66	psi = get_path_selector(name);
	67	if (!psi) {
	68	request_module("dm-%s", name);
	69	psi = get_path_selector(name);
	70	}
	71
	72	return psi ? &psi->pst : NULL;
	73	}
	74
	75	void dm_put_path_selector(struct path_selector_type *pst)
	76	{
	77	struct ps_internal *psi;
	78
	79	if (!pst)
	80	return;
	81
	82	down_read(&_ps_lock);
	83	psi = __find_path_selector_type(pst->name);
	84	if (!psi)
	85	goto out;
	86
	87	if (--psi->use == 0)
	88	module_put(psi->pst.module);
	89
c163c729	90	BUG_ON(psi->use < 0);
1da177e4 LT	91
	92	out:
	93	up_read(&_ps_lock);
	94	}
	95
	96	static struct ps_internal _alloc_path_selector(struct path_selector_type pst)
	97	{
094262db	98	struct ps_internal psi = kzalloc(sizeof(psi), GFP_KERNEL);
1da177e4	99
094262db	100	if (psi)
1da177e4	101	psi->pst = *pst;
1da177e4 LT	102
	103	return psi;
	104	}
	105
	106	int dm_register_path_selector(struct path_selector_type *pst)
	107	{
	108	int r = 0;
	109	struct ps_internal *psi = _alloc_path_selector(pst);
	110
	111	if (!psi)
	112	return -ENOMEM;
	113
	114	down_write(&_ps_lock);
	115
	116	if (__find_path_selector_type(pst->name)) {
	117	kfree(psi);
	118	r = -EEXIST;
	119	} else
	120	list_add(&psi->list, &_path_selectors);
	121
	122	up_write(&_ps_lock);
	123
	124	return r;
	125	}
	126
	127	int dm_unregister_path_selector(struct path_selector_type *pst)
	128	{
	129	struct ps_internal *psi;
	130
	131	down_write(&_ps_lock);
	132
	133	psi = __find_path_selector_type(pst->name);
	134	if (!psi) {
	135	up_write(&_ps_lock);
	136	return -EINVAL;
	137	}
	138
	139	if (psi->use) {
	140	up_write(&_ps_lock);
	141	return -ETXTBSY;
	142	}
	143
	144	list_del(&psi->list);
	145
	146	up_write(&_ps_lock);
	147
	148	kfree(psi);
	149
	150	return 0;
	151	}
	152
	153	EXPORT_SYMBOL_GPL(dm_register_path_selector);
	154	EXPORT_SYMBOL_GPL(dm_unregister_path_selector);