netdev - [PATCH net-next v2 09/12] net-sysfs: remove the rtnl lock when accessing the xps maps

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Message-Id: <20210208171917.1088230-10-atenart@kernel.org>
Date:   Mon,  8 Feb 2021 18:19:14 +0100
From:   Antoine Tenart <atenart@...nel.org>
To:     davem@...emloft.net, kuba@...nel.org, alexander.duyck@...il.com
Cc:     Antoine Tenart <atenart@...nel.org>, netdev@...r.kernel.org
Subject: [PATCH net-next v2 09/12] net-sysfs: remove the rtnl lock when accessing the xps maps

Now that nr_ids and num_tc are stored in the xps dev_maps, which are RCU
protected, we do not have the need to protect the xps_cpus_show and
xps_rxqs_show functions with the rtnl lock.

Signed-off-by: Antoine Tenart <atenart@...nel.org>
---
 net/core/net-sysfs.c | 26 ++++----------------------
 1 file changed, 4 insertions(+), 22 deletions(-)

diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index c2276b589cfb..6ce5772e799e 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -1328,17 +1328,12 @@ static ssize_t xps_cpus_show(struct netdev_queue *queue,
 
 	index = get_netdev_queue_index(queue);
 
-	if (!rtnl_trylock())
-		return restart_syscall();
-
 	/* If queue belongs to subordinate dev use its map */
 	dev = netdev_get_tx_queue(dev, index)->sb_dev ? : dev;
 
 	tc = netdev_txq_to_tc(dev, index);
-	if (tc < 0) {
-		ret = -EINVAL;
-		goto err_rtnl_unlock;
-	}
+	if (tc < 0)
+		return -EINVAL;
 
 	rcu_read_lock();
 	dev_maps = rcu_dereference(dev->xps_maps[XPS_CPUS]);
@@ -1371,16 +1366,12 @@ static ssize_t xps_cpus_show(struct netdev_queue *queue,
 out_no_maps:
 	rcu_read_unlock();
 
-	rtnl_unlock();
-
 	len = bitmap_print_to_pagebuf(false, buf, mask, nr_ids);
 	bitmap_free(mask);
 	return len < PAGE_SIZE ? len : -EINVAL;
 
 err_rcu_unlock:
 	rcu_read_unlock();
-err_rtnl_unlock:
-	rtnl_unlock();
 	return ret;
 }
 
@@ -1435,14 +1426,9 @@ static ssize_t xps_rxqs_show(struct netdev_queue *queue, char *buf)
 
 	index = get_netdev_queue_index(queue);
 
-	if (!rtnl_trylock())
-		return restart_syscall();
-
 	tc = netdev_txq_to_tc(dev, index);
-	if (tc < 0) {
-		ret = -EINVAL;
-		goto err_rtnl_unlock;
-	}
+	if (tc < 0)
+		return -EINVAL;
 
 	rcu_read_lock();
 	dev_maps = rcu_dereference(dev->xps_maps[XPS_RXQS]);
@@ -1475,8 +1461,6 @@ static ssize_t xps_rxqs_show(struct netdev_queue *queue, char *buf)
 out_no_maps:
 	rcu_read_unlock();
 
-	rtnl_unlock();
-
 	len = bitmap_print_to_pagebuf(false, buf, mask, nr_ids);
 	bitmap_free(mask);
 
@@ -1484,8 +1468,6 @@ static ssize_t xps_rxqs_show(struct netdev_queue *queue, char *buf)
 
 err_rcu_unlock:
 	rcu_read_unlock();
-err_rtnl_unlock:
-	rtnl_unlock();
 	return ret;
 }
 
-- 
2.29.2