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Linux/net/rds/loop.c

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  1 /*
  2  * Copyright (c) 2006 Oracle.  All rights reserved.
  3  *
  4  * This software is available to you under a choice of one of two
  5  * licenses.  You may choose to be licensed under the terms of the GNU
  6  * General Public License (GPL) Version 2, available from the file
  7  * COPYING in the main directory of this source tree, or the
  8  * OpenIB.org BSD license below:
  9  *
 10  *     Redistribution and use in source and binary forms, with or
 11  *     without modification, are permitted provided that the following
 12  *     conditions are met:
 13  *
 14  *      - Redistributions of source code must retain the above
 15  *        copyright notice, this list of conditions and the following
 16  *        disclaimer.
 17  *
 18  *      - Redistributions in binary form must reproduce the above
 19  *        copyright notice, this list of conditions and the following
 20  *        disclaimer in the documentation and/or other materials
 21  *        provided with the distribution.
 22  *
 23  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 24  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 25  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 26  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 27  * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 28  * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 29  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 30  * SOFTWARE.
 31  *
 32  */
 33 #include <linux/kernel.h>
 34 #include <linux/slab.h>
 35 #include <linux/in.h>
 36 
 37 #include "rds.h"
 38 #include "loop.h"
 39 
 40 static DEFINE_SPINLOCK(loop_conns_lock);
 41 static LIST_HEAD(loop_conns);
 42 
 43 /*
 44  * This 'loopback' transport is a special case for flows that originate
 45  * and terminate on the same machine.
 46  *
 47  * Connection build-up notices if the destination address is thought of
 48  * as a local address by a transport.  At that time it decides to use the
 49  * loopback transport instead of the bound transport of the sending socket.
 50  *
 51  * The loopback transport's sending path just hands the sent rds_message
 52  * straight to the receiving path via an embedded rds_incoming.
 53  */
 54 
 55 /*
 56  * Usually a message transits both the sender and receiver's conns as it
 57  * flows to the receiver.  In the loopback case, though, the receive path
 58  * is handed the sending conn so the sense of the addresses is reversed.
 59  */
 60 static int rds_loop_xmit(struct rds_connection *conn, struct rds_message *rm,
 61                          unsigned int hdr_off, unsigned int sg,
 62                          unsigned int off)
 63 {
 64         struct scatterlist *sgp = &rm->data.op_sg[sg];
 65         int ret = sizeof(struct rds_header) +
 66                         be32_to_cpu(rm->m_inc.i_hdr.h_len);
 67 
 68         /* Do not send cong updates to loopback */
 69         if (rm->m_inc.i_hdr.h_flags & RDS_FLAG_CONG_BITMAP) {
 70                 rds_cong_map_updated(conn->c_fcong, ~(u64) 0);
 71                 ret = min_t(int, ret, sgp->length - conn->c_xmit_data_off);
 72                 goto out;
 73         }
 74 
 75         BUG_ON(hdr_off || sg || off);
 76 
 77         rds_inc_init(&rm->m_inc, conn, conn->c_laddr);
 78         /* For the embedded inc. Matching put is in loop_inc_free() */
 79         rds_message_addref(rm);
 80 
 81         rds_recv_incoming(conn, conn->c_laddr, conn->c_faddr, &rm->m_inc,
 82                           GFP_KERNEL);
 83 
 84         rds_send_drop_acked(conn, be64_to_cpu(rm->m_inc.i_hdr.h_sequence),
 85                             NULL);
 86 
 87         rds_inc_put(&rm->m_inc);
 88 out:
 89         return ret;
 90 }
 91 
 92 /*
 93  * See rds_loop_xmit(). Since our inc is embedded in the rm, we
 94  * make sure the rm lives at least until the inc is done.
 95  */
 96 static void rds_loop_inc_free(struct rds_incoming *inc)
 97 {
 98         struct rds_message *rm = container_of(inc, struct rds_message, m_inc);
 99         rds_message_put(rm);
100 }
101 
102 /* we need to at least give the thread something to succeed */
103 static int rds_loop_recv(struct rds_connection *conn)
104 {
105         return 0;
106 }
107 
108 struct rds_loop_connection {
109         struct list_head loop_node;
110         struct rds_connection *conn;
111 };
112 
113 /*
114  * Even the loopback transport needs to keep track of its connections,
115  * so it can call rds_conn_destroy() on them on exit. N.B. there are
116  * 1+ loopback addresses (127.*.*.*) so it's not a bug to have
117  * multiple loopback conns allocated, although rather useless.
118  */
119 static int rds_loop_conn_alloc(struct rds_connection *conn, gfp_t gfp)
120 {
121         struct rds_loop_connection *lc;
122         unsigned long flags;
123 
124         lc = kzalloc(sizeof(struct rds_loop_connection), gfp);
125         if (!lc)
126                 return -ENOMEM;
127 
128         INIT_LIST_HEAD(&lc->loop_node);
129         lc->conn = conn;
130         conn->c_transport_data = lc;
131 
132         spin_lock_irqsave(&loop_conns_lock, flags);
133         list_add_tail(&lc->loop_node, &loop_conns);
134         spin_unlock_irqrestore(&loop_conns_lock, flags);
135 
136         return 0;
137 }
138 
139 static void rds_loop_conn_free(void *arg)
140 {
141         struct rds_loop_connection *lc = arg;
142         unsigned long flags;
143 
144         rdsdebug("lc %p\n", lc);
145         spin_lock_irqsave(&loop_conns_lock, flags);
146         list_del(&lc->loop_node);
147         spin_unlock_irqrestore(&loop_conns_lock, flags);
148         kfree(lc);
149 }
150 
151 static int rds_loop_conn_connect(struct rds_connection *conn)
152 {
153         rds_connect_complete(conn);
154         return 0;
155 }
156 
157 static void rds_loop_conn_shutdown(struct rds_connection *conn)
158 {
159 }
160 
161 void rds_loop_exit(void)
162 {
163         struct rds_loop_connection *lc, *_lc;
164         LIST_HEAD(tmp_list);
165 
166         /* avoid calling conn_destroy with irqs off */
167         spin_lock_irq(&loop_conns_lock);
168         list_splice(&loop_conns, &tmp_list);
169         INIT_LIST_HEAD(&loop_conns);
170         spin_unlock_irq(&loop_conns_lock);
171 
172         list_for_each_entry_safe(lc, _lc, &tmp_list, loop_node) {
173                 WARN_ON(lc->conn->c_passive);
174                 rds_conn_destroy(lc->conn);
175         }
176 }
177 
178 /*
179  * This is missing .xmit_* because loop doesn't go through generic
180  * rds_send_xmit() and doesn't call rds_recv_incoming().  .listen_stop and
181  * .laddr_check are missing because transport.c doesn't iterate over
182  * rds_loop_transport.
183  */
184 struct rds_transport rds_loop_transport = {
185         .xmit                   = rds_loop_xmit,
186         .recv                   = rds_loop_recv,
187         .conn_alloc             = rds_loop_conn_alloc,
188         .conn_free              = rds_loop_conn_free,
189         .conn_connect           = rds_loop_conn_connect,
190         .conn_shutdown          = rds_loop_conn_shutdown,
191         .inc_copy_to_user       = rds_message_inc_copy_to_user,
192         .inc_free               = rds_loop_inc_free,
193         .t_name                 = "loopback",
194 };
195 

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