netdev - [PATCH net-next 1/3] devlink: Decrease refcnt of parent rate object on leaf destroy

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Date:   Wed, 23 Jun 2021 16:43:13 +0300
From:   <dlinkin@...dia.com>
To:     <netdev@...r.kernel.org>
CC:     <davem@...emloft.net>, <kuba@...nel.org>, <jiri@...dia.com>,
        <parav@...dia.com>, <vladbu@...dia.com>,
        Dmytro Linkin <dlinkin@...dia.com>
Subject: [PATCH net-next 1/3] devlink: Decrease refcnt of parent rate object on leaf destroy

From: Dmytro Linkin <dlinkin@...dia.com>

Port functions, like SFs, can be deleted by the user when its leaf rate
object has parent node. In such case node refcnt won't be decreased
which blocks the node from deletion later.
Do simple refcnt decrease, since driver in cleanup stage. This:
1) assumes that driver took proper internal parent unset action;
2) allows to avoid nested callbacks call and deadlock.

Fixes: d75559845078 ("devlink: Allow setting parent node of rate objects")
Signed-off-by: Dmytro Linkin <dlinkin@...dia.com>
Reviewed-by: Jiri Pirko <jiri@...dia.com>
---
 net/core/devlink.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/core/devlink.c b/net/core/devlink.c
index 566ddd1..ba27395 100644
--- a/net/core/devlink.c
+++ b/net/core/devlink.c
@@ -9275,6 +9275,8 @@ void devlink_rate_leaf_destroy(struct devlink_port *devlink_port)
 
 	mutex_lock(&devlink->lock);
 	devlink_rate_notify(devlink_rate, DEVLINK_CMD_RATE_DEL);
+	if (devlink_rate->parent)
+		refcount_dec(&devlink_rate->parent->refcnt);
 	list_del(&devlink_rate->list);
 	devlink_port->devlink_rate = NULL;
 	mutex_unlock(&devlink->lock);
-- 
1.8.3.1