linux-kernel - [PATCH v2 2/4] ipmi: msghandler: Add a limit for the number of messages

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Message-ID: <tencent_ADBE84293031AFCF8E409D87E2BE9B0FF507@qq.com>
Date:   Wed, 30 Mar 2022 00:12:40 +0800
From:   Chen Guanqiao <chen.chenchacha@...mail.com>
To:     minyard@....org, openipmi-developer@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org
Cc:     Chen Guanqiao <chen.chenchacha@...mail.com>
Subject: [PATCH v2 2/4] ipmi: msghandler: Add a limit for the number of messages

The administrator sets the limit for the number of messages by modifying
/sys/module/ipmi_msghandler/parameters/default_max_msgs.

Before create a message, count the number of outstanding messages, if
the number reaches the limit, it will return a busy.

Signed-off-by: Chen Guanqiao <chen.chenchacha@...mail.com>
---
 drivers/char/ipmi/ipmi_msghandler.c | 37 +++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/drivers/char/ipmi/ipmi_msghandler.c b/drivers/char/ipmi/ipmi_msghandler.c
index 7886c8337368..80ab88702c5f 100644
--- a/drivers/char/ipmi/ipmi_msghandler.c
+++ b/drivers/char/ipmi/ipmi_msghandler.c
@@ -151,6 +151,12 @@ module_param(default_max_users, uint, 0644);
 MODULE_PARM_DESC(default_max_users,
 		 "The maximum number of users per interface");

+/* The default maximum number of outstanding messages per intf */
+static unsigned int default_max_messages = 100;
+module_param(default_max_messages, uint, 0644);
+MODULE_PARM_DESC(default_max_messages,
+		 "The maximum number of outstanding messages per interface");
+
 /* Call every ~1000 ms. */
 #define IPMI_TIMEOUT_TIME	1000

@@ -916,6 +922,30 @@ unsigned int ipmi_addr_length(int addr_type)
 }
 EXPORT_SYMBOL(ipmi_addr_length);

+static void intf_msg_count(struct ipmi_smi *intf,
+			   unsigned int *hp_count, unsigned int *count)
+{
+	struct ipmi_smi_msg *msg;
+	unsigned long flags;
+	int hp_msg_count = 0, msg_count = 0;
+	int run_to_completion = intf->run_to_completion;
+
+	if (!run_to_completion)
+		spin_lock_irqsave(&intf->xmit_msgs_lock, flags);
+	if (!intf->in_shutdown) {
+		list_for_each_entry(msg, &intf->hp_xmit_msgs, link)
+			hp_msg_count++;
+
+		list_for_each_entry(msg, &intf->xmit_msgs, link)
+			msg_count++;
+	}
+	if (!run_to_completion)
+		spin_unlock_irqrestore(&intf->xmit_msgs_lock, flags);
+
+	*hp_count = hp_msg_count;
+	*count = msg_count;
+}
+
 static int deliver_response(struct ipmi_smi *intf, struct ipmi_recv_msg *msg)
 {
 	int rv = 0;
@@ -2299,6 +2329,7 @@ static int i_ipmi_request(struct ipmi_user     *user,
 {
 	struct ipmi_smi_msg *smi_msg;
 	struct ipmi_recv_msg *recv_msg;
+	unsigned hp_msg_count, msg_count;
 	int rv = 0;

 	if (supplied_recv)
@@ -2330,6 +2361,12 @@ static int i_ipmi_request(struct ipmi_user     *user,
 		goto out_err;
 	}

+	intf_msg_count(intf, &hp_msg_count, &msg_count);
+	if ((hp_msg_count + msg_count) > default_max_messages) {
+		rv = -EBUSY;
+		goto out_err;
+	}
+
 	recv_msg->user = user;
 	if (user)
 		/* The put happens when the message is freed. */
--
2.25.1