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

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On 11/3/18 2:34 AM, Greg Kroah-Hartman wrote:
4.18-stable review patch.  If anyone has any objections, please let me know.


This patch has a problem.  I am working on a fix for that.  Please
do not include it in the stable release.  Thanks.


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

[ 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@xxxxxxxxxx>
Acked-by: Santosh Shilimkar <santosh.shilimkar@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
  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];


--
K. Poon
ka-cheong.poon@xxxxxxxxxx





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