linux-kernel - [PATCH] net: core: devlink.c: Use built-in RCU list checking

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Message-Id: <20200225122745.31095-1-madhuparnabhowmik10@gmail.com>
Date:   Tue, 25 Feb 2020 17:57:45 +0530
From:   madhuparnabhowmik10@...il.com
To:     jiri@...lanox.com, davem@...emloft.net
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        joel@...lfernandes.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        frextrite@...il.com, paulmck@...nel.org,
        Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>
Subject: [PATCH] net: core: devlink.c: Use built-in RCU list checking

From: Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>

list_for_each_entry_rcu() has built-in RCU and lock checking.

Pass cond argument to list_for_each_entry_rcu() to silence
false lockdep warning when CONFIG_PROVE_RCU_LIST is enabled.

The devlink->lock is held when devlink_dpipe_table_find()
is called in non RCU read side section. Therefore, pass struct devlink
to devlink_dpipe_table_find() for lockdep checking.

Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>
---
 net/core/devlink.c | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/net/core/devlink.c b/net/core/devlink.c
index e82750bdc496..a92ab58304e5 100644
--- a/net/core/devlink.c
+++ b/net/core/devlink.c
@@ -2103,11 +2103,11 @@ static int devlink_dpipe_entry_put(struct sk_buff *skb,
 
 static struct devlink_dpipe_table *
 devlink_dpipe_table_find(struct list_head *dpipe_tables,
-			 const char *table_name)
+			 const char *table_name, struct devlink *devlink)
 {
 	struct devlink_dpipe_table *table;
-
-	list_for_each_entry_rcu(table, dpipe_tables, list) {
+	list_for_each_entry_rcu(table, dpipe_tables, list,
+				lockdep_is_held(&devlink->lock)) {
 		if (!strcmp(table->name, table_name))
 			return table;
 	}
@@ -2226,7 +2226,7 @@ static int devlink_nl_cmd_dpipe_entries_get(struct sk_buff *skb,
 
 	table_name = nla_data(info->attrs[DEVLINK_ATTR_DPIPE_TABLE_NAME]);
 	table = devlink_dpipe_table_find(&devlink->dpipe_table_list,
-					 table_name);
+					 table_name, devlink);
 	if (!table)
 		return -EINVAL;
 
@@ -2382,7 +2382,7 @@ static int devlink_dpipe_table_counters_set(struct devlink *devlink,
 	struct devlink_dpipe_table *table;
 
 	table = devlink_dpipe_table_find(&devlink->dpipe_table_list,
-					 table_name);
+					 table_name, devlink);
 	if (!table)
 		return -EINVAL;
 
@@ -6814,7 +6814,7 @@ bool devlink_dpipe_table_counter_enabled(struct devlink *devlink,
 
 	rcu_read_lock();
 	table = devlink_dpipe_table_find(&devlink->dpipe_table_list,
-					 table_name);
+					 table_name, devlink);
 	enabled = false;
 	if (table)
 		enabled = table->counters_enabled;
@@ -6845,7 +6845,8 @@ int devlink_dpipe_table_register(struct devlink *devlink,
 
 	mutex_lock(&devlink->lock);
 
-	if (devlink_dpipe_table_find(&devlink->dpipe_table_list, table_name)) {
+	if (devlink_dpipe_table_find(&devlink->dpipe_table_list, table_name,
+				     devlink)) {
 		err = -EEXIST;
 		goto unlock;
 	}
@@ -6881,7 +6882,7 @@ void devlink_dpipe_table_unregister(struct devlink *devlink,
 
 	mutex_lock(&devlink->lock);
 	table = devlink_dpipe_table_find(&devlink->dpipe_table_list,
-					 table_name);
+					 table_name, devlink);
 	if (!table)
 		goto unlock;
 	list_del_rcu(&table->list);
@@ -7038,7 +7039,7 @@ int devlink_dpipe_table_resource_set(struct devlink *devlink,
 
 	mutex_lock(&devlink->lock);
 	table = devlink_dpipe_table_find(&devlink->dpipe_table_list,
-					 table_name);
+					 table_name, devlink);
 	if (!table) {
 		err = -EINVAL;
 		goto out;
-- 
2.17.1