[RFC PATCH net-next 06/12] drop_monitor: Use pre_doit / post_doit hooks

[Ido Schimmel <idosch@idosch.org>]

From: Ido Schimmel <idosch@mellanox.com>

Each operation from user space should be protected by the global drop
monitor mutex. Use the pre_doit / post_doit hooks to take / release the
lock instead of doing it explicitly in each function.

Signed-off-by: Ido Schimmel <idosch@mellanox.com>
---
 net/core/drop_monitor.c | 24 +++++++++++++++++-------
 1 file changed, 17 insertions(+), 7 deletions(-)

diff --git a/net/core/drop_monitor.c b/net/core/drop_monitor.c
index 1d463c0d4bc5..099000930736 100644
--- a/net/core/drop_monitor.c
+++ b/net/core/drop_monitor.c
@@ -75,6 +75,20 @@ static int dm_delay = 1;
 static unsigned long dm_hw_check_delta = 2*HZ;
 static LIST_HEAD(hw_stats_list);
 
+static int net_dm_nl_pre_doit(const struct genl_ops *ops,
+			      struct sk_buff *skb, struct genl_info *info)
+{
+	mutex_lock(&net_dm_mutex);
+
+	return 0;
+}
+
+static void net_dm_nl_post_doit(const struct genl_ops *ops,
+				struct sk_buff *skb, struct genl_info *info)
+{
+	mutex_unlock(&net_dm_mutex);
+}
+
 static struct sk_buff *reset_per_cpu_data(struct per_cpu_dm_data *data)
 {
 	size_t al;
@@ -247,12 +261,9 @@ static int set_all_monitor_traces(int state, struct netlink_ext_ack *extack)
 	struct dm_hw_stat_delta *new_stat = NULL;
 	struct dm_hw_stat_delta *temp;
 
-	mutex_lock(&net_dm_mutex);
-
 	if (state == trace_state) {
 		NL_SET_ERR_MSG_MOD(extack, "Trace state already set to requested state");
-		rc = -EAGAIN;
-		goto out_unlock;
+		return -EAGAIN;
 	}
 
 	switch (state) {
@@ -296,9 +307,6 @@ static int set_all_monitor_traces(int state, struct netlink_ext_ack *extack)
 	else
 		rc = -EINPROGRESS;
 
-out_unlock:
-	mutex_unlock(&net_dm_mutex);
-
 	return rc;
 }
 
@@ -384,6 +392,8 @@ static struct genl_family net_drop_monitor_family __ro_after_init = {
 	.hdrsize        = 0,
 	.name           = "NET_DM",
 	.version        = 2,
+	.pre_doit	= net_dm_nl_pre_doit,
+	.post_doit	= net_dm_nl_post_doit,
 	.module		= THIS_MODULE,
 	.ops		= dropmon_ops,
 	.n_ops		= ARRAY_SIZE(dropmon_ops),
-- 
2.21.0