[Devel] [PATCH RHEL7 COMMIT] ms/drop_monitor: Add alert mode operations

[Konstantin Khorenko]

The commit is pushed to "branch-rh7-3.10.0-1160.66.1.vz7.188.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-1160.66.1.vz7.188.6
------>
commit 88fcf81f58f95767a96ac41bc5bc11b0412ce9f4
Author: Ido Schimmel <idosch at mellanox.com>
Date:   Mon Jul 4 21:52:01 2022 +0300

    ms/drop_monitor: Add alert mode operations
    
    The next patch is going to add another alert mode in which the dropped
    packet is notified to user space, instead of only a summary of recent
    drops.
    
    Abstract the differences between the modes by adding alert mode
    operations. The operations are selected based on the currently
    configured mode and associated with the probes and the work item just
    before tracing starts.
    
    Signed-off-by: Ido Schimmel <idosch at mellanox.com>
    Signed-off-by: David S. Miller <davem at davemloft.net>
    (cherry picked from commit 28315f7999870bb56da236f6b4ffce63efcc7897)
    
    Adapted. napi_poll_probe callback prototype was changed.
    1db19db7 ("net: tracepoint napi:napi_poll add work and budget ")
    
    Signed-off-by: Alexander Mikhalitsyn <alexander.mikhalitsyn at virtuozzo.com>
    
    =================
    Patchset description:
    drop_monitor: Add packet alert mode
    
    Just port and adapt packet alert mode feature for RHEL7 kernel.
    
    https://jira.sw.ru/browse/PSBM-140937
    
    Ported-by: Alexander Mikhalitsyn <alexander.mikhalitsyn at virtuozzo.com>
---
 include/uapi/linux/net_dropmon.h |  9 +++++++++
 net/core/drop_monitor.c          | 37 +++++++++++++++++++++++++++++++------
 2 files changed, 40 insertions(+), 6 deletions(-)

diff --git a/include/uapi/linux/net_dropmon.h b/include/uapi/linux/net_dropmon.h
index 2a739462caeb3..855d96c197b43 100644
--- a/include/uapi/linux/net_dropmon.h
+++ b/include/uapi/linux/net_dropmon.h
@@ -61,4 +61,13 @@ enum {
  * Our group identifiers
  */
 #define NET_DM_GRP_ALERT 1
+
+/**
+ * enum net_dm_alert_mode - Alert mode.
+ * @NET_DM_ALERT_MODE_SUMMARY: A summary of recent drops is sent to user space.
+ */
+enum net_dm_alert_mode {
+	NET_DM_ALERT_MODE_SUMMARY,
+};
+
 #endif
diff --git a/net/core/drop_monitor.c b/net/core/drop_monitor.c
index 309f525004086..c3f591d69f301 100644
--- a/net/core/drop_monitor.c
+++ b/net/core/drop_monitor.c
@@ -74,6 +74,15 @@ static int dm_delay = 1;
 static unsigned long dm_hw_check_delta = 2*HZ;
 static LIST_HEAD(hw_stats_list);
 
+static enum net_dm_alert_mode net_dm_alert_mode = NET_DM_ALERT_MODE_SUMMARY;
+
+struct net_dm_alert_ops {
+	void (*kfree_skb_probe)(void *ignore, struct sk_buff *skb,
+				void *location);
+	void (*napi_poll_probe)(void *ignore, struct napi_struct *napi);
+	void (*work_item_func)(struct work_struct *work);
+};
+
 static struct sk_buff *reset_per_cpu_data(struct per_cpu_dm_data *data)
 {
 	size_t al;
@@ -239,10 +248,23 @@ static void trace_napi_poll_hit(void *ignore, struct napi_struct *napi)
 	rcu_read_unlock();
 }
 
+static const struct net_dm_alert_ops net_dm_alert_summary_ops = {
+	.kfree_skb_probe	= trace_kfree_skb_hit,
+	.napi_poll_probe	= trace_napi_poll_hit,
+	.work_item_func		= send_dm_alert,
+};
+
+static const struct net_dm_alert_ops *net_dm_alert_ops_arr[] = {
+	[NET_DM_ALERT_MODE_SUMMARY]	= &net_dm_alert_summary_ops,
+};
+
 static int net_dm_trace_on_set(void)
 {
+	const struct net_dm_alert_ops *ops;
 	int cpu, rc;
 
+	ops = net_dm_alert_ops_arr[net_dm_alert_mode];
+
 	if (!try_module_get(THIS_MODULE))
 		return -ENODEV;
 
@@ -250,7 +272,7 @@ static int net_dm_trace_on_set(void)
 		struct per_cpu_dm_data *data = &per_cpu(dm_cpu_data, cpu);
 		struct sk_buff *skb;
 
-		INIT_WORK(&data->dm_alert_work, send_dm_alert);
+		INIT_WORK(&data->dm_alert_work, ops->work_item_func);
 		timer_setup(&data->send_timer, sched_send_work, 0);
 		/* Allocate a new per-CPU skb for the summary alert message and
 		 * free the old one which might contain stale data from
@@ -260,18 +282,18 @@ static int net_dm_trace_on_set(void)
 		consume_skb(skb);
 	}
 
-	rc = register_trace_kfree_skb(trace_kfree_skb_hit, NULL);
+	rc = register_trace_kfree_skb(ops->kfree_skb_probe, NULL);
 	if (rc)
 		goto err_module_put;
 
-	rc = register_trace_napi_poll(trace_napi_poll_hit, NULL);
+	rc = register_trace_napi_poll(ops->napi_poll_probe, NULL);
 	if (rc)
 		goto err_unregister_trace;
 
 	return 0;
 
 err_unregister_trace:
-	unregister_trace_kfree_skb(trace_kfree_skb_hit, NULL);
+	unregister_trace_kfree_skb(ops->kfree_skb_probe, NULL);
 err_module_put:
 	module_put(THIS_MODULE);
 	return rc;
@@ -280,10 +302,13 @@ static int net_dm_trace_on_set(void)
 static void net_dm_trace_off_set(void)
 {
 	struct dm_hw_stat_delta *new_stat, *temp;
+	const struct net_dm_alert_ops *ops;
 	int cpu;
 
-	unregister_trace_napi_poll(trace_napi_poll_hit, NULL);
-	unregister_trace_kfree_skb(trace_kfree_skb_hit, NULL);
+	ops = net_dm_alert_ops_arr[net_dm_alert_mode];
+
+	unregister_trace_napi_poll(ops->napi_poll_probe, NULL);
+	unregister_trace_kfree_skb(ops->kfree_skb_probe, NULL);
 
 	tracepoint_synchronize_unregister();