path: root/drivers/md/dm-log.c

/*
 * Copyright (C) 2003 Sistina Software
 * Copyright (C) 2004-2008 Red Hat, Inc. All rights reserved.
 *
 * This file is released under the LGPL.
 */

#include <linux/init.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/vmalloc.h>
#include <linux/dm-io.h>
#include <linux/dm-dirty-log.h>

#include <linux/device-mapper.h>

#define DM_MSG_PREFIX "dirty region log"

struct dm_dirty_log_internal {
	struct dm_dirty_log_type *type;

	struct list_head list;
	long use;
};

static LIST_HEAD(_log_types);
static DEFINE_SPINLOCK(_lock);

static struct dm_dirty_log_internal *__find_dirty_log_type(const char *name)
{
	struct dm_dirty_log_internal *log_type;

	list_for_each_entry(log_type, &_log_types, list)
		if (!strcmp(name, log_type->type->name))
			return log_type;

	return NULL;
}

static struct dm_dirty_log_internal *_get_dirty_log_type(const char *name)
{
	struct dm_dirty_log_internal *log_type;

	spin_lock(&_lock);

	log_type = __find_dirty_log_type(name);
	if (log_type) {
		if (!log_type->use && !try_module_get(log_type->type->module))
			log_type = NULL;
		else
			log_type->use++;
	}

	spin_unlock(&_lock);

	return log_type;
}

/*
 * get_type
 * @type_name
 *
 * Attempt to retrieve the dm_dirty_log_type by name.  If not already
 * available, attempt to load the appropriate module.
 *
 * Log modules are named "dm-log-" followed by the 'type_name'.
 * Modules may contain multiple types.
 * This function will first try the module "dm-log-<type_name>",
 * then truncate 'type_name' on the last '-' and try again.
 *
 * For example, if type_name was "clustered-disk", it would search
 * 'dm-log-clustered-disk' then 'dm-log-clustered'.
 *
 * Returns: dirty_log_type* on success, NULL on failure
 */
static struct dm_dirty_log_type *get_type(const char *type_name)
{
	char *p, *type_name_dup;
	struct dm_dirty_log_internal *log_type;

	if (!type_name)
		return NULL;

	log_type = _get_dirty_log_type(type_name);
	if (log_type)
		return log_type->type;

	type_name_dup = kstrdup(type_name, GFP_KERNEL);
	if (!type_name_dup) {
		DMWARN("No memory left to attempt log module load for \"%s\"",
		       type_name);
		return NULL;
	}

	while (request_module("dm-log-%s", type_name_dup) ||
	       !(log_type = _get_dirty_log_type(type_name))) {
		p = strrchr(type_name_dup, '-');
		if (!p)
			break;
		p[0] = '\0';
	}

	if (!log_type)
		DMWARN("Module for logging type \"%s\" not found.", type_name);

	kfree(type_name_dup);

	return log_type ? log_type->type : NULL;
}

static void put_type(struct dm_dirty_log_type *type)
{
	struct dm_dirty_log_internal *log_type;

	if (!type)
		return;

	spin_lock(&_lock);
	log_type = __find_dirty_log_type(type->name);
	if (!log_type)
		goto out;

	if (!--log_type->use)
		module_put(type->module);

	BUG_ON(log_type->use < 0);

out:
	spin_unlock(&_lock);
}

static struct dm_dirty_log_internal *_alloc_dirty_log_type(struct dm_dirty_log_type *type)
{
	struct dm_dirty_log_internal *log_type = kzalloc(sizeof(*log_type),
							 GFP_KERNEL);

	if (log_type)
		log_type->type = type;

	return log_type;
}

int dm_dirty_log_type_register(struct dm_dirty_log_type *type)
{
	struct dm_dirty_log_internal *log_type = _alloc_dirty_log_type(type);
	int r = 0;

	if (!log_type)
		return -ENOMEM;

	spin_lock(&_lock);
	if (!__find_dirty_log_type(type->name))
		list_add(&log_type->list, &_log_types);
	else {
		kfree(log_type);
		r = -EEXIST;
	}
	spin_unlock(&_lock);

	return r;
}
EXPORT_SYMBOL(dm_dirty_log_type_register);

int dm_dirty_log_type_unregister(struct dm_dirty_log_type *type)
{
	struct dm_dirty_log_internal *log_type;

	spin_lock(&_lock);

	log_type = __find_dirty_log_type(type->name);
	if (!log_type) {
		spin_unlock(&_lock);
		return -EINVAL;
	}

	if (log_type->use) {
		spin_unlock(&_lock);
		return -ETXTBSY;
	}

	list_del(&log_type->list);

	spin_unlock(&_lock);
	kfree(log_type);

	return 0;
}
EXPORT_SYMBOL(dm_dirty_log_type_unregister);

struct dm_dirty_log *dm_dirty_log_create(const char *type_name,
					 struct dm_target *ti,
					 unsigned int argc, char **argv)
{
	struct dm_dirty_log_type *type;
	struct dm_dirty_log *log;

	log = kmalloc(sizeof(*log), GFP_KERNEL);
	if (!log)
		return NULL;

	type = get_type(type_name);
	if (!type) {
		kfree(log);
		return NULL;
	}

	log->type = type;
	if (type->ctr(log, ti, argc, argv)) {
		kfree(log);