linux-kernel - [PATCH 3.16 094/328] IB/IPoIB: Set ah valid flag in multicast send flow

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Message-ID: <lsq.1544392233.850406480@decadent.org.uk>
Date:   Sun, 09 Dec 2018 21:50:33 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Jason Gunthorpe" <jgg@...lanox.com>,
        "Leon Romanovsky" <leonro@...lanox.com>,
        "Denis Drozdov" <denisd@...lanox.com>,
        "Feras Daoud" <ferasda@...lanox.com>,
        "Erez Shitrit" <erezsh@...lanox.com>
Subject: [PATCH 3.16 094/328] IB/IPoIB: Set ah valid flag in multicast
 send flow

3.16.62-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Denis Drozdov <denisd@...lanox.com>

commit 75da96067ade4e7854379ec2f7834f3497652b1a upstream.

The change of ipoib_ah data structure with adding "valid" flag and
checks of ah->valid in ipoib_start_xmit affected multicast packet flow.

Since the multicast flow doesn't invoke path_rec_start, "ah->valid" flag
remains unset, so that ipoib_start_xmit end up with neigh_refresh_path
instead of sending the packet using neigh.

"ah->valid" has to be set in multicast send flow. As a result IPoIB
starts sending packets via neigh immediately and eliminates 60sec delay
of neigh keep alive interval.

The typical example of this issue are two sequential arpings:

arping 11.134.208.9 -> got response (mcast_send)
arping 11.134.208.9 -> no response  (ah->valid = 0)

Fixes: fa9391dbad4b ("RDMA/ipoib: Update paths on CLIENT_REREG/SM_CHANGE events")
Signed-off-by: Denis Drozdov <denisd@...lanox.com>
Reviewed-by: Erez Shitrit <erezsh@...lanox.com>
Reviewed-by: Feras Daoud <ferasda@...lanox.com>
Signed-off-by: Leon Romanovsky <leonro@...lanox.com>
Signed-off-by: Jason Gunthorpe <jgg@...lanox.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/infiniband/ulp/ipoib/ipoib_multicast.c | 1 +
 1 file changed, 1 insertion(+)

--- a/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
+++ b/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
@@ -734,6 +734,7 @@ out:
 			if (neigh && list_empty(&neigh->list)) {
 				kref_get(&mcast->ah->ref);
 				neigh->ah	= mcast->ah;
+				neigh->ah->valid = 1;
 				list_add_tail(&neigh->list, &mcast->neigh_list);
 			}
 		}