From: Ido Schimmel <idosch@mellanox.com>
Date: Sun, 11 Aug 2019 10:35:54 +0300
Subject: drop_monitor: Make drop queue length configurable
Patch-mainline: v5.4-rc1
Git-commit: 30328d46af593dcf24582f2a431d84ea0cf4bdef
References: bsc#1154353

In packet alert mode, each CPU holds a list of dropped skbs that need to
be processed in process context and sent to user space. To avoid
exhausting the system's memory the maximum length of this queue is
currently set to 1000.

Allow users to tune the length of this queue according to their needs.
The configured length is reported to user space when drop monitor
configuration is queried.

Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 include/uapi/linux/net_dropmon.h |    1 +
 net/core/drop_monitor.c          |   19 ++++++++++++++++---
 2 files changed, 17 insertions(+), 3 deletions(-)

--- a/include/uapi/linux/net_dropmon.h
+++ b/include/uapi/linux/net_dropmon.h
@@ -79,6 +79,7 @@ enum net_dm_attr {
 	NET_DM_ATTR_PAD,
 	NET_DM_ATTR_TRUNC_LEN,			/* u32 */
 	NET_DM_ATTR_ORIG_LEN,			/* u32 */
+	NET_DM_ATTR_QUEUE_LEN,			/* u32 */
 
 	__NET_DM_ATTR_MAX,
 	NET_DM_ATTR_MAX = __NET_DM_ATTR_MAX - 1
--- a/net/core/drop_monitor.c
+++ b/net/core/drop_monitor.c
@@ -78,6 +78,7 @@ static LIST_HEAD(hw_stats_list);
 
 static enum net_dm_alert_mode net_dm_alert_mode = NET_DM_ALERT_MODE_SUMMARY;
 static u32 net_dm_trunc_len;
+static u32 net_dm_queue_len = 1000;
 
 struct net_dm_alert_ops {
 	void (*kfree_skb_probe)(void *ignore, struct sk_buff *skb,
@@ -93,8 +94,6 @@ struct net_dm_skb_cb {
 
 #define NET_DM_SKB_CB(__skb) ((struct net_dm_skb_cb *)&((__skb)->cb[0]))
 
-#define NET_DM_QUEUE_LEN 1000
-
 static struct sk_buff *reset_per_cpu_data(struct per_cpu_dm_data *data)
 {
 	size_t al;
@@ -289,7 +288,7 @@ static void net_dm_packet_trace_kfree_sk
 	data = this_cpu_ptr(&dm_cpu_data);
 
 	spin_lock_irqsave(&data->drop_queue.lock, flags);
-	if (skb_queue_len(&data->drop_queue) < NET_DM_QUEUE_LEN)
+	if (skb_queue_len(&data->drop_queue) < net_dm_queue_len)
 		__skb_queue_tail(&data->drop_queue, nskb);
 	else
 		goto unlock_free;
@@ -643,6 +642,14 @@ static void net_dm_trunc_len_set(struct
 	net_dm_trunc_len = nla_get_u32(info->attrs[NET_DM_ATTR_TRUNC_LEN]);
 }
 
+static void net_dm_queue_len_set(struct genl_info *info)
+{
+	if (!info->attrs[NET_DM_ATTR_QUEUE_LEN])
+		return;
+
+	net_dm_queue_len = nla_get_u32(info->attrs[NET_DM_ATTR_QUEUE_LEN]);
+}
+
 static int net_dm_cmd_config(struct sk_buff *skb,
 			struct genl_info *info)
 {
@@ -660,6 +667,8 @@ static int net_dm_cmd_config(struct sk_b
 
 	net_dm_trunc_len_set(info);
 
+	net_dm_queue_len_set(info);
+
 	return 0;
 }
 
@@ -691,6 +700,9 @@ static int net_dm_config_fill(struct sk_
 	if (nla_put_u32(msg, NET_DM_ATTR_TRUNC_LEN, net_dm_trunc_len))
 		goto nla_put_failure;
 
+	if (nla_put_u32(msg, NET_DM_ATTR_QUEUE_LEN, net_dm_queue_len))
+		goto nla_put_failure;
+
 	genlmsg_end(msg, hdr);
 
 	return 0;
@@ -763,6 +775,7 @@ static const struct nla_policy net_dm_nl
 	[NET_DM_ATTR_UNSPEC] = { .strict_start_type = NET_DM_ATTR_UNSPEC + 1 },
 	[NET_DM_ATTR_ALERT_MODE] = { .type = NLA_U8 },
 	[NET_DM_ATTR_TRUNC_LEN] = { .type = NLA_U32 },
+	[NET_DM_ATTR_QUEUE_LEN] = { .type = NLA_U32 },
 };
 
 static const struct genl_ops dropmon_ops[] = {