netdev - [PATCH net-next 06/14] devlink: Add device lock assert in reload operation

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Date: Wed, 15 Nov 2023 13:17:15 +0100
From: Petr Machata <petrm@...dia.com>
To: "David S. Miller" <davem@...emloft.net>, Eric Dumazet
	<edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
	<pabeni@...hat.com>, <netdev@...r.kernel.org>
CC: Ido Schimmel <idosch@...dia.com>, Petr Machata <petrm@...dia.com>, "Amit
 Cohen" <amcohen@...dia.com>, <mlxsw@...dia.com>, Jiri Pirko <jiri@...dia.com>
Subject: [PATCH net-next 06/14] devlink: Add device lock assert in reload operation

From: Ido Schimmel <idosch@...dia.com>

Add an assert to verify that the device lock is always held throughout
reload operations.

Tested the following flows with netdevsim and mlxsw while lockdep is
enabled:

netdevsim:

 # echo "10 1" > /sys/bus/netdevsim/new_device
 # devlink dev reload netdevsim/netdevsim10
 # ip netns add bla
 # devlink dev reload netdevsim/netdevsim10 netns bla
 # ip netns del bla
 # echo 10 > /sys/bus/netdevsim/del_device

mlxsw:

 # devlink dev reload pci/0000:01:00.0
 # ip netns add bla
 # devlink dev reload pci/0000:01:00.0 netns bla
 # ip netns del bla
 # echo 1 > /sys/bus/pci/devices/0000\:01\:00.0/remove
 # echo 1 > /sys/bus/pci/rescan

Signed-off-by: Ido Schimmel <idosch@...dia.com>
Reviewed-by: Jiri Pirko <jiri@...dia.com>
Signed-off-by: Petr Machata <petrm@...dia.com>
---
 net/devlink/dev.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/net/devlink/dev.c b/net/devlink/dev.c
index 4fc7adb32663..ea6a92f2e6a2 100644
--- a/net/devlink/dev.c
+++ b/net/devlink/dev.c
@@ -4,6 +4,7 @@
  * Copyright (c) 2016 Jiri Pirko <jiri@...lanox.com>
  */
 
+#include <linux/device.h>
 #include <net/genetlink.h>
 #include <net/sock.h>
 #include "devl_internal.h"
@@ -433,6 +434,13 @@ int devlink_reload(struct devlink *devlink, struct net *dest_net,
 	struct net *curr_net;
 	int err;
 
+	/* Make sure the reload operations are invoked with the device lock
+	 * held to allow drivers to trigger functionality that expects it
+	 * (e.g., PCI reset) and to close possible races between these
+	 * operations and probe/remove.
+	 */
+	device_lock_assert(devlink->dev);
+
 	memcpy(remote_reload_stats, devlink->stats.remote_reload_stats,
 	       sizeof(remote_reload_stats));
 
-- 
2.41.0