netdev - [PATCH] rds: avoid unenecessary cong

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Date:   Thu, 14 Jun 2018 11:52:34 -0700
From:   Santosh Shilimkar <santosh.shilimkar@...cle.com>
To:     netdev@...r.kernel.org, davem@...emloft.net
Cc:     Santosh Shilimkar <santosh.shilimkar@...cle.com>
Subject: [PATCH] rds: avoid unenecessary cong_update in loop transport

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@...kaller.appspotmail.com
Reviewed-by: Sowmini Varadhan <sowmini.varadhan@...cle.com>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@...cle.com>
---
 net/rds/loop.c | 1 +
 net/rds/rds.h  | 5 +++++
 net/rds/recv.c | 5 +++++
 3 files changed, 11 insertions(+)

diff --git a/net/rds/loop.c b/net/rds/loop.c
index f2bf78d..dac6218 100644
--- a/net/rds/loop.c
+++ b/net/rds/loop.c
@@ -193,4 +193,5 @@ 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,
 };
diff --git a/net/rds/rds.h b/net/rds/rds.h
index b04c333..f2272fb 100644
--- a/net/rds/rds.h
+++ b/net/rds/rds.h
@@ -479,6 +479,11 @@ 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
  *
diff --git a/net/rds/recv.c b/net/rds/recv.c
index dc67458..192ac6f 100644
--- a/net/rds/recv.c
+++ b/net/rds/recv.c
@@ -103,6 +103,11 @@ static void rds_recv_rcvbuf_delta(struct rds_sock *rs, struct sock *sk,
 		rds_stats_add(s_recv_bytes_added_to_socket, delta);
 	else
 		rds_stats_add(s_recv_bytes_removed_from_socket, -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 "
-- 
1.9.1