RDS: Add TCP transport to RDS

This code allows RDS to be tunneled over a TCP connection.

RDMA operations are disabled when using TCP transport,
but this frees RDS from the IB/RDMA stack dependency, and allows
it to be used with standard Ethernet adapters, or in a VM.

Signed-off-by: Andy Grover <andy.grover@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 263 insertions, 0 deletions

diff --git a/net/rds/tcp_send.c b/net/rds/tcp_send.c
new file mode 100644
index 000000000000..ab545e0cd5d6
--- /dev/null
+++ b/net/rds/tcp_send.c
@@ -0,0 +1,263 @@
+/*
+ * 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/in.h>
+#include <net/tcp.h>
+
+#include "rds.h"
+#include "tcp.h"
+
+static void rds_tcp_cork(struct socket *sock, int val)
+{
+	mm_segment_t oldfs;
+
+	oldfs = get_fs();
+	set_fs(KERNEL_DS);
+	sock->ops->setsockopt(sock, SOL_TCP, TCP_CORK, (char __user *)&val,
+			      sizeof(val));
+	set_fs(oldfs);
+}
+
+void rds_tcp_xmit_prepare(struct rds_connection *conn)
+{
+	struct rds_tcp_connection *tc = conn->c_transport_data;
+
+	rds_tcp_cork(tc->t_sock, 1);
+}
+
+void rds_tcp_xmit_complete(struct rds_connection *conn)
+{
+	struct rds_tcp_connection *tc = conn->c_transport_data;
+
+	rds_tcp_cork(tc->t_sock, 0);
+}
+
+/* the core send_sem serializes this with other xmit and shutdown */
+int rds_tcp_sendmsg(struct socket *sock, void *data, unsigned int len)
+{
+	struct kvec vec = {
+                .iov_base = data,
+                .iov_len = len,
+	};
+        struct msghdr msg = {
+                .msg_flags = MSG_DONTWAIT | MSG_NOSIGNAL,
+        };
+
+	return kernel_sendmsg(sock, &msg, &vec, 1, vec.iov_len);
+}
+
+/* the core send_sem serializes this with other xmit and shutdown */
+int rds_tcp_xmit_cong_map(struct rds_connection *conn,
+			  struct rds_cong_map *map, unsigned long offset)
+{
+	static struct rds_header rds_tcp_map_header = {
+		.h_flags = RDS_FLAG_CONG_BITMAP,
+	};
+	struct rds_tcp_connection *tc = conn->c_transport_data;
+	unsigned long i;
+	int ret;
+	int copied = 0;
+
+	/* Some problem claims cpu_to_be32(constant) isn't a constant. */
+	rds_tcp_map_header.h_len = cpu_to_be32(RDS_CONG_MAP_BYTES);
+
+	if (offset < sizeof(struct rds_header)) {
+		ret = rds_tcp_sendmsg(tc->t_sock,
+				      (void *)&rds_tcp_map_header + offset,
+				      sizeof(struct rds_header) - offset);
+		if (ret <= 0)
+			return ret;
+		offset += ret;
+		copied = ret;
+		if (offset < sizeof(struct rds_header))
+			return ret;
+	}
+
+	offset -= sizeof(struct rds_header);
+	i = offset / PAGE_SIZE;
+	offset = offset % PAGE_SIZE;
+	BUG_ON(i >= RDS_CONG_MAP_PAGES);
+
+	do {
+		ret = tc->t_sock->ops->sendpage(tc->t_sock,
+					virt_to_page(map->m_page_addrs[i]),
+					offset, PAGE_SIZE - offset,
+					MSG_DONTWAIT);
+		if (ret <= 0)
+			break;
+		copied += ret;
+		offset += ret;
+		if (offset == PAGE_SIZE) {
+			offset = 0;
+			i++;
+		}
+	} while (i < RDS_CONG_MAP_PAGES);
+
+        return copied ? copied : ret;
+}
+
+/* the core send_sem serializes this with other xmit and shutdown */
+int rds_tcp_xmit(struct rds_connection *conn, struct rds_message *rm,
+	         unsigned int hdr_off, unsigned int sg, unsigned int off)
+{
+	struct rds_tcp_connection *tc = conn->c_transport_data;
+	int done = 0;
+	int ret = 0;
+
+	if (hdr_off == 0) {
+		/*
+		 * m_ack_seq is set to the sequence number of the last byte of
+		 * header and data.  see rds_tcp_is_acked().
+		 */
+		tc->t_last_sent_nxt = rds_tcp_snd_nxt(tc);
+		rm->m_ack_seq = tc->t_last_sent_nxt +
+				sizeof(struct rds_header) +
+				be32_to_cpu(rm->m_inc.i_hdr.h_len) - 1;
+		smp_mb__before_clear_bit();
+		set_bit(RDS_MSG_HAS_ACK_SEQ, &rm->m_flags);
+		tc->t_last_expected_una = rm->m_ack_seq + 1;
+
+		rdsdebug("rm %p tcp nxt %u ack_seq %llu\n",
+			 rm, rds_tcp_snd_nxt(tc),
+			 (unsigned long long)rm->m_ack_seq);
+	}
+
+	if (hdr_off < sizeof(struct rds_header)) {
+		/* see rds_tcp_write_space() */
+		set_bit(SOCK_NOSPACE, &tc->t_sock->sk->sk_socket->flags);
+
+		ret = rds_tcp_sendmsg(tc->t_sock,
+				      (void *)&rm->m_inc.i_hdr + hdr_off,
+				      sizeof(rm->m_inc.i_hdr) - hdr_off);
+		if (ret < 0)
+			goto out;
+		done += ret;
+		if (hdr_off + done != sizeof(struct rds_header))
+			goto out;
+	}
+
+	while (sg < rm->m_nents) {
+		ret = tc->t_sock->ops->sendpage(tc->t_sock,
+						sg_page(&rm->m_sg[sg]),
+						rm->m_sg[sg].offset + off,
+						rm->m_sg[sg].length - off,
+						MSG_DONTWAIT|MSG_NOSIGNAL);
+		rdsdebug("tcp sendpage %p:%u:%u ret %d\n", (void *)sg_page(&rm->m_sg[sg]),
+			 rm->m_sg[sg].offset + off, rm->m_sg[sg].length - off,
+			 ret);
+		if (ret <= 0)
+			break;
+
+		off += ret;
+		done += ret;
+		if (off == rm->m_sg[sg].length) {
+			off = 0;
+			sg++;
+		}
+	}
+
+out:
+	if (ret <= 0) {
+		/* write_space will hit after EAGAIN, all else fatal */
+		if (ret == -EAGAIN) {
+			rds_tcp_stats_inc(s_tcp_sndbuf_full);
+			ret = 0;
+		} else {
+			printk(KERN_WARNING "RDS/tcp: send to %u.%u.%u.%u "
+			       "returned %d, disconnecting and reconnecting\n",
+			       NIPQUAD(conn->c_faddr), ret);
+			rds_conn_drop(conn);
+		}
+	}
+	if (done == 0)
+		done = ret;
+	return done;
+}
+
+/*
+ * rm->m_ack_seq is set to the tcp sequence number that corresponds to the
+ * last byte of the message, including the header.  This means that the
+ * entire message has been received if rm->m_ack_seq is "before" the next
+ * unacked byte of the TCP sequence space.  We have to do very careful
+ * wrapping 32bit comparisons here.
+ */
+static int rds_tcp_is_acked(struct rds_message *rm, uint64_t ack)
+{
+	if (!test_bit(RDS_MSG_HAS_ACK_SEQ, &rm->m_flags))
+		return 0;
+	return (__s32)((u32)rm->m_ack_seq - (u32)ack) < 0;
+}
+
+void rds_tcp_write_space(struct sock *sk)
+{
+	void (*write_space)(struct sock *sk);
+	struct rds_connection *conn;
+	struct rds_tcp_connection *tc;
+
+	read_lock(&sk->sk_callback_lock);
+	conn = sk->sk_user_data;
+	if (conn == NULL) {
+		write_space = sk->sk_write_space;
+		goto out;
+	}
+
+	tc = conn->c_transport_data;
+	rdsdebug("write_space for tc %p\n", tc);
+	write_space = tc->t_orig_write_space;
+	rds_tcp_stats_inc(s_tcp_write_space_calls);
+
+	rdsdebug("tcp una %u\n", rds_tcp_snd_una(tc));
+	tc->t_last_seen_una = rds_tcp_snd_una(tc);
+	rds_send_drop_acked(conn, rds_tcp_snd_una(tc), rds_tcp_is_acked);
+
+	queue_delayed_work(rds_wq, &conn->c_send_w, 0);
+out:
+	read_unlock(&sk->sk_callback_lock);
+
+	/*
+	 * write_space is only called when data leaves tcp's send queue if
+	 * SOCK_NOSPACE is set.  We set SOCK_NOSPACE every time we put
+	 * data in tcp's send queue because we use write_space to parse the
+	 * sequence numbers and notice that rds messages have been fully
+	 * received.
+	 *
+	 * tcp's write_space clears SOCK_NOSPACE if the send queue has more
+	 * than a certain amount of space. So we need to set it again *after*
+	 * we call tcp's write_space or else we might only get called on the
+	 * first of a series of incoming tcp acks.
+	 */
+	write_space(sk);
+
+	if (sk->sk_socket)
+		set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
+}