linux-kernel - [PATCH 5.12 495/700] RDMA/cma: Fix incorrect Packet Lifetime calculation

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Date:   Mon, 12 Jul 2021 08:09:38 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Håkon Bugge <haakon.bugge@...cle.com>,
        Leon Romanovsky <leonro@...dia.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.12 495/700] RDMA/cma: Fix incorrect Packet Lifetime calculation

From: Håkon Bugge <haakon.bugge@...cle.com>

[ Upstream commit e84045eab69c625bc0b0bf24d8e05bc65da1eed1 ]

An approximation for the PacketLifeTime is half the local ACK timeout.
The encoding for both timers are logarithmic.

If the local ACK timeout is set, but zero, it means the timer is
disabled. In this case, we choose the CMA_IBOE_PACKET_LIFETIME value,
since 50% of infinite makes no sense.

Before this commit, the PacketLifeTime became 255 if local ACK
timeout was zero (not running).

Fixed by explicitly testing for timeout being zero.

Fixes: e1ee1e62bec4 ("RDMA/cma: Use ACK timeout for RoCE packetLifeTime")
Link: https://lore.kernel.org/r/1624371207-26710-1-git-send-email-haakon.bugge@oracle.com
Signed-off-by: Håkon Bugge <haakon.bugge@...cle.com>
Reviewed-by: Leon Romanovsky <leonro@...dia.com>
Signed-off-by: Jason Gunthorpe <jgg@...dia.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/infiniband/core/cma.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/infiniband/core/cma.c b/drivers/infiniband/core/cma.c
index 2f5f384987a2..68bbcecb0a6a 100644
--- a/drivers/infiniband/core/cma.c
+++ b/drivers/infiniband/core/cma.c
@@ -3060,8 +3060,10 @@ static int cma_resolve_iboe_route(struct rdma_id_private *id_priv)
 	 * as a reasonable approximation for RoCE networks.
 	 */
 	mutex_lock(&id_priv->qp_mutex);
-	route->path_rec->packet_life_time = id_priv->timeout_set ?
-		id_priv->timeout - 1 : CMA_IBOE_PACKET_LIFETIME;
+	if (id_priv->timeout_set && id_priv->timeout)
+		route->path_rec->packet_life_time = id_priv->timeout - 1;
+	else
+		route->path_rec->packet_life_time = CMA_IBOE_PACKET_LIFETIME;
 	mutex_unlock(&id_priv->qp_mutex);
 
 	if (!route->path_rec->mtu) {
-- 
2.30.2