FS-Cache: Provide a slab for cookie allocation

[net-next-2.6.git] / fs / fscache / cookie.c

/* netfs cookie management
 *
 * Copyright (C) 2004-2007 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#define FSCACHE_DEBUG_LEVEL COOKIE
#include <linux/module.h>
#include <linux/slab.h>
#include "internal.h"

struct kmem_cache *fscache_cookie_jar;

/*
 * initialise an cookie jar slab element prior to any use
 */
void fscache_cookie_init_once(void *_cookie)
{
	struct fscache_cookie *cookie = _cookie;

	memset(cookie, 0, sizeof(*cookie));
	spin_lock_init(&cookie->lock);
	INIT_HLIST_HEAD(&cookie->backing_objects);
}

/*
 * destroy a cookie
 */
void __fscache_cookie_put(struct fscache_cookie *cookie)
{
	struct fscache_cookie *parent;

	_enter("%p", cookie);

	for (;;) {
		_debug("FREE COOKIE %p", cookie);
		parent = cookie->parent;
		BUG_ON(!hlist_empty(&cookie->backing_objects));
		kmem_cache_free(fscache_cookie_jar, cookie);

		if (!parent)
			break;

		cookie = parent;
		BUG_ON(atomic_read(&cookie->usage) <= 0);
		if (!atomic_dec_and_test(&cookie->usage))
			break;
	}

	_leave("");
}