1. 根目录:
2. net
3. rds
4. transport.c

/*
 * Copyright (c) 2006 Oracle.  All rights reserved.
 *
 * This software is available to you under a choice of one of two
 * licenses.  You may choose to be licensed under the terms of the GNU
 * General Public License (GPL) Version 2, available from the file
 * COPYING in the main directory of this source tree, or the
 * OpenIB.org BSD license below:
 *
 *     Redistribution and use in source and binary forms, with or
 *     without modification, are permitted provided that the following
 *     conditions are met:
 *
 *      - Redistributions of source code must retain the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer.
 *
 *      - Redistributions in binary form must reproduce the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer in the documentation and/or other materials
 *        provided with the distribution.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 *
 */
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/in.h>

#include "rds.h"
#include "loop.h"

static struct rds_transport *transports[RDS_TRANS_COUNT];
static DECLARE_RWSEM(rds_trans_sem);

int rds_trans_register(struct rds_transport *trans)
{
	BUG_ON(strlen(trans->t_name) + 1 > TRANSNAMSIZ);

	down_write(&rds_trans_sem);

	if (transports[trans->t_type])
		printk(KERN_ERR "RDS Transport type %d already registered\n",
			trans->t_type);
	else {
		transports[trans->t_type] = trans;
		printk(KERN_INFO "Registered RDS/%s transport\n", trans->t_name);
	}

	up_write(&rds_trans_sem);

	return 0;
}
EXPORT_SYMBOL_GPL(rds_trans_register);

void rds_trans_unregister(struct rds_transport *trans)
{
	down_write(&rds_trans_sem);

	transports[trans->t_type] = NULL;
	printk(KERN_INFO "Unregistered RDS/%s transport\n", trans->t_name);

	up_write(&rds_trans_sem);
}
EXPORT_SYMBOL_GPL(rds_trans_unregister);

void rds_trans_put(struct rds_transport *trans)
{
	if (trans)
		module_put(trans->t_owner);
}

struct rds_transport *rds_trans_get_preferred(struct net *net, __be32 addr)
{
	struct rds_transport *ret = NULL;
	struct rds_transport *trans;
	unsigned int i;

	if (IN_LOOPBACK(ntohl(addr)))
		return &rds_loop_transport;

	down_read(&rds_trans_sem);
	for (i = 0; i < RDS_TRANS_COUNT; i++) {
		trans = transports[i];

		if (trans && (trans->laddr_check(net, addr) == 0) &&
		    (!trans->t_owner || try_module_get(trans->t_owner))) {
			ret = trans;
			break;
		}
	}
	up_read(&rds_trans_sem);

	return ret;
}

struct rds_transport *rds_trans_get(int t_type)
{
	struct rds_transport *ret = NULL;
	struct rds_transport *trans;
	unsigned int i;

	down_read(&rds_trans_sem);
	for (i = 0; i < RDS_TRANS_COUNT; i++) {
		trans = transports[i];

		if (trans && trans->t_type == t_type &&
		    (!trans->t_owner || try_module_get(trans->t_owner))) {
			ret = trans;
			break;
		}
	}
	up_read(&rds_trans_sem);

	return ret;
}

/*
 * This returns the number of stats entries in the snapshot and only
 * copies them using the iter if there is enough space for them.  The
 * caller passes in the global stats so that we can size and copy while
 * holding the lock.
 */
unsigned int rds_trans_stats_info_copy(struct rds_info_iterator *iter,
				       unsigned int avail)

{
	struct rds_transport *trans;
	unsigned int total = 0;
	unsigned int part;
	int i;

	rds_info_iter_unmap(iter);
	down_read(&rds_trans_sem);

	for (i = 0; i < RDS_TRANS_COUNT; i++)
	{
		trans = transports[i];
		if (!trans || !trans->stats_info_copy)
			continue;

		part = trans->stats_info_copy(iter, avail);
		avail -= min(avail, part);
		total += part;
	}

	up_read(&rds_trans_sem);

	return total;
}