diff mbox series

[v2,2/2] net: devinet: Reduce refcount before grace period

Message ID 20221118191909.1756624-2-joel@joelfernandes.org
State New
Headers
Series [v2,1/2] net: Use call_rcu_flush() for dst_destroy_rcu |

Commit Message

Joel Fernandes Nov. 18, 2022, 7:19 p.m. UTC 
  From: Eric Dumazet <edumazet@google.com>

Currently, the inetdev_destroy() function waits for an RCU grace period
before decrementing the refcount and freeing memory. This causes a delay
with a new RCU configuration that tries to save power, which results in the
network interface disappearing later than expected. The resulting delay
causes test failures on ChromeOS.

Refactor the code such that the refcount is freed before the grace period
and memory is freed after. With this a ChromeOS network test passes that
does 'ip netns del' and polls for an interface disappearing, now passes.

Reported-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
---
 net/ipv4/devinet.c | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

Comments

Paul E. McKenney Nov. 18, 2022, 10:23 p.m. UTC | #1 
On Fri, Nov 18, 2022 at 07:19:09PM +0000, Joel Fernandes (Google) wrote:
> From: Eric Dumazet <edumazet@google.com>
> 
> Currently, the inetdev_destroy() function waits for an RCU grace period
> before decrementing the refcount and freeing memory. This causes a delay
> with a new RCU configuration that tries to save power, which results in the
> network interface disappearing later than expected. The resulting delay
> causes test failures on ChromeOS.
> 
> Refactor the code such that the refcount is freed before the grace period
> and memory is freed after. With this a ChromeOS network test passes that
> does 'ip netns del' and polls for an interface disappearing, now passes.
> 
> Reported-by: Joel Fernandes (Google) <joel@joelfernandes.org>
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>

Queued and pushed, thank you both!

This patch can go as-is based on Eric's Signed-off-by, but the first
one of course needs at least an ack.

							Thanx, Paul

> ---
>  net/ipv4/devinet.c | 19 ++++++++++---------
>  1 file changed, 10 insertions(+), 9 deletions(-)
> 
> diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
> index e8b9a9202fec..b0acf6e19aed 100644
> --- a/net/ipv4/devinet.c
> +++ b/net/ipv4/devinet.c
> @@ -234,13 +234,20 @@ static void inet_free_ifa(struct in_ifaddr *ifa)
>  	call_rcu(&ifa->rcu_head, inet_rcu_free_ifa);
>  }
>  
> +static void in_dev_free_rcu(struct rcu_head *head)
> +{
> +	struct in_device *idev = container_of(head, struct in_device, rcu_head);
> +
> +	kfree(rcu_dereference_protected(idev->mc_hash, 1));
> +	kfree(idev);
> +}
> +
>  void in_dev_finish_destroy(struct in_device *idev)
>  {
>  	struct net_device *dev = idev->dev;
>  
>  	WARN_ON(idev->ifa_list);
>  	WARN_ON(idev->mc_list);
> -	kfree(rcu_dereference_protected(idev->mc_hash, 1));
>  #ifdef NET_REFCNT_DEBUG
>  	pr_debug("%s: %p=%s\n", __func__, idev, dev ? dev->name : "NIL");
>  #endif
> @@ -248,7 +255,7 @@ void in_dev_finish_destroy(struct in_device *idev)
>  	if (!idev->dead)
>  		pr_err("Freeing alive in_device %p\n", idev);
>  	else
> -		kfree(idev);
> +		call_rcu(&idev->rcu_head, in_dev_free_rcu);
>  }
>  EXPORT_SYMBOL(in_dev_finish_destroy);
>  
> @@ -298,12 +305,6 @@ static struct in_device *inetdev_init(struct net_device *dev)
>  	goto out;
>  }
>  
> -static void in_dev_rcu_put(struct rcu_head *head)
> -{
> -	struct in_device *idev = container_of(head, struct in_device, rcu_head);
> -	in_dev_put(idev);
> -}
> -
>  static void inetdev_destroy(struct in_device *in_dev)
>  {
>  	struct net_device *dev;
> @@ -328,7 +329,7 @@ static void inetdev_destroy(struct in_device *in_dev)
>  	neigh_parms_release(&arp_tbl, in_dev->arp_parms);
>  	arp_ifdown(dev);
>  
> -	call_rcu(&in_dev->rcu_head, in_dev_rcu_put);
> +	in_dev_put(in_dev);
>  }
>  
>  int inet_addr_onlink(struct in_device *in_dev, __be32 a, __be32 b)
> -- 
> 2.38.1.584.g0f3c55d4c2-goog
>
diff mbox series

Patch

diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index e8b9a9202fec..b0acf6e19aed 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -234,13 +234,20 @@  static void inet_free_ifa(struct in_ifaddr *ifa)
 	call_rcu(&ifa->rcu_head, inet_rcu_free_ifa);
 }
 
+static void in_dev_free_rcu(struct rcu_head *head)
+{
+	struct in_device *idev = container_of(head, struct in_device, rcu_head);
+
+	kfree(rcu_dereference_protected(idev->mc_hash, 1));
+	kfree(idev);
+}
+
 void in_dev_finish_destroy(struct in_device *idev)
 {
 	struct net_device *dev = idev->dev;
 
 	WARN_ON(idev->ifa_list);
 	WARN_ON(idev->mc_list);
-	kfree(rcu_dereference_protected(idev->mc_hash, 1));
 #ifdef NET_REFCNT_DEBUG
 	pr_debug("%s: %p=%s\n", __func__, idev, dev ? dev->name : "NIL");
 #endif
@@ -248,7 +255,7 @@  void in_dev_finish_destroy(struct in_device *idev)
 	if (!idev->dead)
 		pr_err("Freeing alive in_device %p\n", idev);
 	else
-		kfree(idev);
+		call_rcu(&idev->rcu_head, in_dev_free_rcu);
 }
 EXPORT_SYMBOL(in_dev_finish_destroy);
 
@@ -298,12 +305,6 @@  static struct in_device *inetdev_init(struct net_device *dev)
 	goto out;
 }
 
-static void in_dev_rcu_put(struct rcu_head *head)
-{
-	struct in_device *idev = container_of(head, struct in_device, rcu_head);
-	in_dev_put(idev);
-}
-
 static void inetdev_destroy(struct in_device *in_dev)
 {
 	struct net_device *dev;
@@ -328,7 +329,7 @@  static void inetdev_destroy(struct in_device *in_dev)
 	neigh_parms_release(&arp_tbl, in_dev->arp_parms);
 	arp_ifdown(dev);
 
-	call_rcu(&in_dev->rcu_head, in_dev_rcu_put);
+	in_dev_put(in_dev);
 }
 
 int inet_addr_onlink(struct in_device *in_dev, __be32 a, __be32 b)