[PATCH net v2] connector: Change the judgment conditions for clearing proc_event_num_listeners

[wangkeqi]

From: wangkeqi <wangkeqiwang@xxxxxxxxxxxxxx>

It is inaccurate to judge whether proc_event_num_listeners is
cleared by cn_netlink_send_mult returning -ESRCH.
In the case of stress-ng netlink-proc, -ESRCH will always be returned,
because netlink_broadcast_filtered will return -ESRCH,
which may cause stress-ng netlink-proc performance degradation.
Therefore, the judgment condition is modified to whether
there is a listener.

Reported-by: kernel test robot <oliver.sang@xxxxxxxxx>
Closes: https://lore.kernel.org/oe-lkp/202401112259.b23a1567-oliver.sang@xxxxxxxxx
Fixes: c46bfba133 ("connector: Fix proc_event_num_listeners count not cleared")
Signed-off-by: wangkeqi <wangkeqiwang@xxxxxxxxxxxxxx>
Cc: fengwei.yin@xxxxxxxxx
---
 drivers/connector/cn_proc.c   | 6 ++++--
 drivers/connector/connector.c | 6 ++++++
 include/linux/connector.h     | 1 +
 3 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/connector/cn_proc.c b/drivers/connector/cn_proc.c
index 3d5e6d705..b09f74ed3 100644
--- a/drivers/connector/cn_proc.c
+++ b/drivers/connector/cn_proc.c
@@ -108,8 +108,10 @@ static inline void send_msg(struct cn_msg *msg)
 		filter_data[1] = 0;
 	}
 
-	if (cn_netlink_send_mult(msg, msg->len, 0, CN_IDX_PROC, GFP_NOWAIT,
-			     cn_filter, (void *)filter_data) == -ESRCH)
+	if (netlink_has_listeners(get_cdev_nls(), CN_IDX_PROC))
+		cn_netlink_send_mult(msg, msg->len, 0, CN_IDX_PROC, GFP_NOWAIT,
+			     cn_filter, (void *)filter_data);
+	else
 		atomic_set(&proc_event_num_listeners, 0);
 
 	local_unlock(&local_event.lock);
diff --git a/drivers/connector/connector.c b/drivers/connector/connector.c
index 7f7b94f61..1b2cd410e 100644
--- a/drivers/connector/connector.c
+++ b/drivers/connector/connector.c
@@ -129,6 +129,12 @@ int cn_netlink_send(struct cn_msg *msg, u32 portid, u32 __group,
 }
 EXPORT_SYMBOL_GPL(cn_netlink_send);
 
+struct sock *get_cdev_nls(void)
+{
+	return cdev.nls;
+}
+EXPORT_SYMBOL_GPL(get_cdev_nls);
+
 /*
  * Callback helper - queues work and setup destructor for given data.
  */
diff --git a/include/linux/connector.h b/include/linux/connector.h
index cec2d99ae..255466aea 100644
--- a/include/linux/connector.h
+++ b/include/linux/connector.h
@@ -127,6 +127,7 @@ int cn_netlink_send_mult(struct cn_msg *msg, u16 len, u32 portid,
  */
 int cn_netlink_send(struct cn_msg *msg, u32 portid, u32 group, gfp_t gfp_mask);
 
+struct sock *get_cdev_nls(void);
 int cn_queue_add_callback(struct cn_queue_dev *dev, const char *name,
 			  const struct cb_id *id,
 			  void (*callback)(struct cn_msg *, struct netlink_skb_parms *));
-- 
2.27.0