linux-kernel - [PATCH 4.18 093/150] rds: RDS (tcp) hangs on sendto() to unresponding address

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Date:   Fri,  2 Nov 2018 19:34:15 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Ka-Cheong Poon <ka-cheong.poon@...cle.com>,
        Santosh Shilimkar <santosh.shilimkar@...cle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.18 093/150] rds: RDS (tcp) hangs on sendto() to unresponding address

4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

[ Upstream commit 9a4890bd6d6325a1c88564a20ab310b2d56f6094 ]

In rds_send_mprds_hash(), if the calculated hash value is non-zero and
the MPRDS connections are not yet up, it will wait.  But it should not
wait if the send is non-blocking.  In this case, it should just use the
base c_path for sending the message.

Signed-off-by: Ka-Cheong Poon <ka-cheong.poon@...cle.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@...cle.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 net/rds/send.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/net/rds/send.c b/net/rds/send.c
index 59f17a2335f4..0e54ca0f4e9e 100644
--- a/net/rds/send.c
+++ b/net/rds/send.c
@@ -1006,7 +1006,8 @@ static int rds_cmsg_send(struct rds_sock *rs, struct rds_message *rm,
 	return ret;
 }
 
-static int rds_send_mprds_hash(struct rds_sock *rs, struct rds_connection *conn)
+static int rds_send_mprds_hash(struct rds_sock *rs,
+			       struct rds_connection *conn, int nonblock)
 {
 	int hash;
 
@@ -1022,10 +1023,16 @@ static int rds_send_mprds_hash(struct rds_sock *rs, struct rds_connection *conn)
 		 * used.  But if we are interrupted, we have to use the zero
 		 * c_path in case the connection ends up being non-MP capable.
 		 */
-		if (conn->c_npaths == 0)
+		if (conn->c_npaths == 0) {
+			/* Cannot wait for the connection be made, so just use
+			 * the base c_path.
+			 */
+			if (nonblock)
+				return 0;
 			if (wait_event_interruptible(conn->c_hs_waitq,
 						     conn->c_npaths != 0))
 				hash = 0;
+		}
 		if (conn->c_npaths == 1)
 			hash = 0;
 	}
@@ -1170,7 +1177,7 @@ int rds_sendmsg(struct socket *sock, struct msghdr *msg, size_t payload_len)
 	}
 
 	if (conn->c_trans->t_mp_capable)
-		cpath = &conn->c_path[rds_send_mprds_hash(rs, conn)];
+		cpath = &conn->c_path[rds_send_mprds_hash(rs, conn, nonblock)];
 	else
 		cpath = &conn->c_path[0];
 
-- 
2.17.1