[linux-2.6-block.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 "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);

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