netdev - Re: [PATCH net-next] Avoid traversing addrconf hash on ifdown

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Message-ID: <20241107223048.17156-1-kuniyu@amazon.com>
Date: Thu, 7 Nov 2024 14:30:48 -0800
From: Kuniyuki Iwashima <kuniyu@...zon.com>
To: <gnaaman@...venets.com>
CC: <davem@...emloft.net>, <dsahern@...nel.org>, <edumazet@...gle.com>,
	<horms@...nel.org>, <kuba@...nel.org>, <netdev@...r.kernel.org>,
	<pabeni@...hat.com>
Subject: Re: [PATCH net-next] Avoid traversing addrconf hash on ifdown

From: Gilad Naaman <gnaaman@...venets.com>
Date: Thu,  7 Nov 2024 16:13:23 +0000
> struct inet6_dev already has a list of addresses owned by the device,
> enabling us to traverse this much shorter list, instead of scanning
> the entire hash-table.
> 
> Signed-off-by: Gilad Naaman <gnaaman@...venets.com>
> ---
>  net/ipv6/addrconf.c | 36 ++++++++++++++++--------------------
>  1 file changed, 16 insertions(+), 20 deletions(-)
> 
> diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
> index d0a99710d65d..9c57c993e1ec 100644
> --- a/net/ipv6/addrconf.c
> +++ b/net/ipv6/addrconf.c
> @@ -3846,12 +3846,12 @@ static int addrconf_ifdown(struct net_device *dev, bool unregister)
>  {
>  	unsigned long event = unregister ? NETDEV_UNREGISTER : NETDEV_DOWN;
>  	struct net *net = dev_net(dev);
> -	struct inet6_dev *idev;
>  	struct inet6_ifaddr *ifa;
>  	LIST_HEAD(tmp_addr_list);
> +	struct inet6_dev *idev;
>  	bool keep_addr = false;
>  	bool was_ready;
> -	int state, i;
> +	int state;
>  
>  	ASSERT_RTNL();
>  
> @@ -3890,28 +3890,24 @@ static int addrconf_ifdown(struct net_device *dev, bool unregister)
>  	}
>  
>  	/* Step 2: clear hash table */
> -	for (i = 0; i < IN6_ADDR_HSIZE; i++) {
> -		struct hlist_head *h = &net->ipv6.inet6_addr_lst[i];
> +	read_lock_bh(&idev->lock);
> +	spin_lock_bh(&net->ipv6.addrconf_hash_lock);

No need to nest _bh.


>  
> -		spin_lock_bh(&net->ipv6.addrconf_hash_lock);
> -restart:
> -		hlist_for_each_entry_rcu(ifa, h, addr_lst) {
> -			if (ifa->idev == idev) {
> -				addrconf_del_dad_work(ifa);
> -				/* combined flag + permanent flag decide if
> -				 * address is retained on a down event
> -				 */
> -				if (!keep_addr ||
> -				    !(ifa->flags & IFA_F_PERMANENT) ||
> -				    addr_is_local(&ifa->addr)) {
> -					hlist_del_init_rcu(&ifa->addr_lst);
> -					goto restart;
> -				}
> -			}
> +	list_for_each_entry(ifa, &idev->addr_list, if_list) {
> +		addrconf_del_dad_work(ifa);

while at it, please add newline here


> +		/* combined flag + permanent flag decide if
> +		 * address is retained on a down event
> +		 */
> +		if (!keep_addr ||
> +		    !(ifa->flags & IFA_F_PERMANENT) ||
> +		    addr_is_local(&ifa->addr)) {
> +			hlist_del_init_rcu(&ifa->addr_lst);
>  		}

and remove unnecessary {}.


> -		spin_unlock_bh(&net->ipv6.addrconf_hash_lock);
>  	}
>  
> +	spin_unlock_bh(&net->ipv6.addrconf_hash_lock);
> +	read_unlock_bh(&idev->lock);
> +
>  	write_lock_bh(&idev->lock);
>  
>  	addrconf_del_rs_timer(idev);
> -- 
> 2.34.1
>