[PATCH 3.18 28/29] rds: avoid unenecessary cong_update in loop transport

From: Greg Kroah-Hartman
Date: Fri Jul 20 2018 - 08:26:18 EST


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

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

From: Santosh Shilimkar <santosh.shilimkar@xxxxxxxxxx>

commit f1693c63ab133d16994cc50f773982b5905af264 upstream.

Loop transport which is self loopback, remote port congestion
update isn't relevant. Infact the xmit path already ignores it.
Receive path needs to do the same.

Reported-by: syzbot+4c20b3866171ce8441d2@xxxxxxxxxxxxxxxxxxxxxxxxx
Reviewed-by: Sowmini Varadhan <sowmini.varadhan@xxxxxxxxxx>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
net/rds/loop.c | 1 +
net/rds/rds.h | 5 +++++
net/rds/recv.c | 5 +++++
3 files changed, 11 insertions(+)

--- a/net/rds/loop.c
+++ b/net/rds/loop.c
@@ -191,4 +191,5 @@ struct rds_transport rds_loop_transport
.inc_copy_to_user = rds_message_inc_copy_to_user,
.inc_free = rds_loop_inc_free,
.t_name = "loopback",
+ .t_type = RDS_TRANS_LOOP,
};
--- a/net/rds/rds.h
+++ b/net/rds/rds.h
@@ -381,6 +381,11 @@ struct rds_notifier {
int n_status;
};

+/* Available as part of RDS core, so doesn't need to participate
+ * in get_preferred transport etc
+ */
+#define RDS_TRANS_LOOP 3
+
/**
* struct rds_transport - transport specific behavioural hooks
*
--- a/net/rds/recv.c
+++ b/net/rds/recv.c
@@ -76,6 +76,11 @@ static void rds_recv_rcvbuf_delta(struct
return;

rs->rs_rcv_bytes += delta;
+
+ /* loop transport doesn't send/recv congestion updates */
+ if (rs->rs_transport->t_type == RDS_TRANS_LOOP)
+ return;
+
now_congested = rs->rs_rcv_bytes > rds_sk_rcvbuf(rs);

rdsdebug("rs %p (%pI4:%u) recv bytes %d buf %d "