/*
 * GPL HEADER START
 *
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 only,
 * as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License version 2 for more details (a copy is included
 * in the LICENSE file that accompanied this code).
 *
 * You should have received a copy of the GNU General Public License
 * version 2 along with this program; If not, see
 * http://www.sun.com/software/products/lustre/docs/GPLv2.pdf
 *
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
 * CA 95054 USA or visit www.sun.com if you need additional information or
 * have any questions.
 *
 * GPL HEADER END
 */
/*
 * Copyright (c) 2003, 2010, Oracle and/or its affiliates. All rights reserved.
 * Use is subject to license terms.
 *
 * Copyright (c) 2011, Whamcloud, Inc.
 */
/*
 * This file is part of Lustre, http://www.lustre.org/
 * Lustre is a trademark of Sun Microsystems, Inc.
 *
 * lustre/obdclass/lustre_handles.c
 *
 * Author: Phil Schwan <phil@clusterfs.com>
 */

#define DEBUG_SUBSYSTEM S_CLASS
#ifndef __KERNEL__
# include <liblustre.h>
#endif

#include <obd_support.h>
#include <lustre_handles.h>
#include <lustre_lib.h>

#ifndef __KERNEL__
# define list_add_rcu            cfs_list_add
# define list_del_rcu            cfs_list_del
# define list_for_each_rcu       cfs_list_for_each
# define list_for_each_safe_rcu  cfs_list_for_each_safe
# define list_for_each_entry_rcu cfs_list_for_each_entry
# define rcu_read_lock()         spin_lock(&bucket->lock)
# define rcu_read_unlock()       spin_unlock(&bucket->lock)
#endif /* !__KERNEL__ */

static __u64 handle_base;
#define HANDLE_INCR 7
static spinlock_t handle_base_lock;

static struct handle_bucket {
	spinlock_t	lock;
	cfs_list_t	head;
} *handle_hash;

#ifdef __arch_um__
/* For unknown reason, UML uses kmalloc rather than vmalloc to allocate
 * memory(OBD_VMALLOC). Therefore, we have to redefine the
 * HANDLE_HASH_SIZE to make the hash heads don't exceed 128K.
 */
#define HANDLE_HASH_SIZE 4096
#else
#define HANDLE_HASH_SIZE (1 << 16)
#endif /* ifdef __arch_um__ */

#define HANDLE_HASH_MASK (HANDLE_HASH_SIZE - 1)

/*
 * Generate a unique 64bit cookie (hash) for a handle and insert it into
 * global (per-node) hash-table.
 */
void class_handle_hash(struct portals_handle *h,
		       struct portals_handle_ops *ops)
{
        struct handle_bucket *bucket;
        ENTRY;

        LASSERT(h != NULL);
        LASSERT(cfs_list_empty(&h->h_link));

        /*
         * This is fast, but simplistic cookie generation algorithm, it will
         * need a re-do at some point in the future for security.
         */
	spin_lock(&handle_base_lock);
	handle_base += HANDLE_INCR;

	h->h_cookie = handle_base;
	if (unlikely(handle_base == 0)) {
		/*
		 * Cookie of zero is "dangerous", because in many places it's
		 * assumed that 0 means "unassigned" handle, not bound to any
		 * object.
		 */
		CWARN("The universe has been exhausted: cookie wrap-around.\n");
		handle_base += HANDLE_INCR;
	}
	spin_unlock(&handle_base_lock);

	h->h_ops = ops;
	spin_lock_init(&h->h_lock);

	bucket = &handle_hash[h->h_cookie & HANDLE_HASH_MASK];
	spin_lock(&bucket->lock);
	list_add_rcu(&h->h_link, &bucket->head);
	h->h_in = 1;
	spin_unlock(&bucket->lock);

	CDEBUG(D_INFO, "added object %p with handle "LPX64" to hash\n",
	       h, h->h_cookie);
	EXIT;
}
EXPORT_SYMBOL(class_handle_hash);

static void class_handle_unhash_nolock(struct portals_handle *h)
{
        if (cfs_list_empty(&h->h_link)) {
                CERROR("removing an already-removed handle ("LPX64")\n",
                       h->h_cookie);
                return;
        }

        CDEBUG(D_INFO, "removing object %p with handle "LPX64" from hash\n",
               h, h->h_cookie);

	spin_lock(&h->h_lock);
	if (h->h_in == 0) {
		spin_unlock(&h->h_lock);
		return;
	}
	h->h_in = 0;
	spin_unlock(&h->h_lock);
	list_del_rcu(&h->h_link);
}

void class_handle_unhash(struct portals_handle *h)
{
	struct handle_bucket *bucket;
	bucket = handle_hash + (h->h_cookie & HANDLE_HASH_MASK);

	spin_lock(&bucket->lock);
	class_handle_unhash_nolock(h);
	spin_unlock(&bucket->lock);
}
EXPORT_SYMBOL(class_handle_unhash);

void class_handle_hash_back(struct portals_handle *h)
{
	struct handle_bucket *bucket;
	ENTRY;

	bucket = handle_hash + (h->h_cookie & HANDLE_HASH_MASK);

	spin_lock(&bucket->lock);
	list_add_rcu(&h->h_link, &bucket->head);
	h->h_in = 1;
	spin_unlock(&bucket->lock);

	EXIT;
}
EXPORT_SYMBOL(class_handle_hash_back);

void *class_handle2object(__u64 cookie)
{
        struct handle_bucket *bucket;
        struct portals_handle *h;
        void *retval = NULL;
        ENTRY;

        LASSERT(handle_hash != NULL);

	/* Be careful when you want to change this code. See the
	 * rcu_read_lock() definition on top this file. - jxiong */
        bucket = handle_hash + (cookie & HANDLE_HASH_MASK);

        rcu_read_lock();
        list_for_each_entry_rcu(h, &bucket->head, h_link) {
                if (h->h_cookie != cookie)
                        continue;

		spin_lock(&h->h_lock);
		if (likely(h->h_in != 0)) {
			h->h_ops->hop_addref(h);
			retval = h;
		}
		spin_unlock(&h->h_lock);
		break;
	}
	rcu_read_unlock();

	RETURN(retval);
}
EXPORT_SYMBOL(class_handle2object);

void class_handle_free_cb(cfs_rcu_head_t *rcu)
{
	struct portals_handle *h = RCU2HANDLE(rcu);
	void *ptr = (void *)(unsigned long)h->h_cookie;

	if (h->h_ops->hop_free != NULL)
		h->h_ops->hop_free(ptr, h->h_size);
	else
		OBD_FREE(ptr, h->h_size);
}
EXPORT_SYMBOL(class_handle_free_cb);

int class_handle_init(void)
{
        struct handle_bucket *bucket;
        struct timeval tv;
        int seed[2];

        LASSERT(handle_hash == NULL);

        OBD_ALLOC_LARGE(handle_hash, sizeof(*bucket) * HANDLE_HASH_SIZE);
        if (handle_hash == NULL)
                return -ENOMEM;

	spin_lock_init(&handle_base_lock);
	for (bucket = handle_hash + HANDLE_HASH_SIZE - 1; bucket >= handle_hash;
	     bucket--) {
		CFS_INIT_LIST_HEAD(&bucket->head);
		spin_lock_init(&bucket->lock);
	}

        /** bug 21430: add randomness to the initial base */
        cfs_get_random_bytes(seed, sizeof(seed));
        cfs_gettimeofday(&tv);
        cfs_srand(tv.tv_sec ^ seed[0], tv.tv_usec ^ seed[1]);

        cfs_get_random_bytes(&handle_base, sizeof(handle_base));
        LASSERT(handle_base != 0ULL);

        return 0;
}

static int cleanup_all_handles(void)
{
	int rc;
	int i;

	for (rc = i = 0; i < HANDLE_HASH_SIZE; i++) {
		struct portals_handle *h;

		spin_lock(&handle_hash[i].lock);
		list_for_each_entry_rcu(h, &(handle_hash[i].head), h_link) {
			CERROR("force clean handle "LPX64" addr %p ops %p\n",
			       h->h_cookie, h, h->h_ops);

			class_handle_unhash_nolock(h);
			rc++;
		}
		spin_unlock(&handle_hash[i].lock);
	}

	return rc;
}

void class_handle_cleanup(void)
{
        int count;
        LASSERT(handle_hash != NULL);

        count = cleanup_all_handles();

        OBD_FREE_LARGE(handle_hash, sizeof(*handle_hash) * HANDLE_HASH_SIZE);
        handle_hash = NULL;

        if (count != 0)
                CERROR("handle_count at cleanup: %d\n", count);
}