Subject: Re: [PATCH v2 net-next 1/6] bonding: add rcu to vlan_uses_dev() and make bond_vlan_used() use it

From: Nikolay Aleksandrov <[email-masked]>
Date: Fri, 09 Aug 2013 13:06:51 +0200

On 08/08/2013 06:57 PM, Veaceslav Falico wrote:
> RFC -> v1: don't add vlan_uses_dev_rcu() and change vlan_uses_dev() instead
> v1  -> v2: remove the ASSERT_RTNL(), cause we can now be called under rcu.
> 
> Currently, bond_vlan_used() looks for any vlan, including the pseudo-vlan
> id 0, and always returns true if 8021q is loaded. This creates several bad
> situations - some warnings in __bond_release_one() because it thinks that
> we still have vlans while removing, sending LB packets with vlan id 0 and,
> possibly, other caused by vlan id 0.
> 
> Fix it by changing vlan_uses_dev() to use rcu_dereference_rtnl() instead of
> rtnl_dereference(), and thus it can already be used in bond_vlan_used()
> under rcu_read_lock().
> 
> By the time vlan_uses_dev() returns we cannot be sure if there were no
> vlans added/removed, so it's basicly an optimization function.
> 
> Also, use the vlan_uses_dev() in __bond_release_one() cause the rtnl lock
> is held there.
> 
> For this call to be visible in bonding.h, add include <linux/if_vlan.h>,
> and also remove it from any other bonding file, cause they all include
> bonding.h, and thus linux/if_vlan.h.
> 
> CC: Jay Vosburgh <[email-masked]>
> CC: Andy Gospodarek <[email-masked]>
> CC: Patrick McHardy <[email-masked]>
> CC: "David S. Miller" <[email-masked]>
> CC: Nikolay Aleksandrov <[email-masked]>
> Signed-off-by: Veaceslav Falico <[email-masked]>
> ---
>  drivers/net/bonding/bond_alb.c  |    1 -
>  drivers/net/bonding/bond_main.c |    3 +--
>  drivers/net/bonding/bonding.h   |   10 +++++++++-
>  net/8021q/vlan_core.c           |    5 ++---
>  4 files changed, 12 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/net/bonding/bond_alb.c b/drivers/net/bonding/bond_alb.c
> index 3a5db7b..2684329 100644
> --- a/drivers/net/bonding/bond_alb.c
> +++ b/drivers/net/bonding/bond_alb.c
> @@ -34,7 +34,6 @@
>  #include <linux/if_arp.h>
>  #include <linux/if_ether.h>
>  #include <linux/if_bonding.h>
> -#include <linux/if_vlan.h>
>  #include <linux/in.h>
>  #include <net/ipx.h>
>  #include <net/arp.h>
> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
> index 4264a76..9d1045d 100644
> --- a/drivers/net/bonding/bond_main.c
> +++ b/drivers/net/bonding/bond_main.c
> @@ -69,7 +69,6 @@
>  #include <net/arp.h>
>  #include <linux/mii.h>
>  #include <linux/ethtool.h>
> -#include <linux/if_vlan.h>
>  #include <linux/if_bonding.h>
>  #include <linux/jiffies.h>
>  #include <linux/preempt.h>
> @@ -1953,7 +1952,7 @@ static int __bond_release_one(struct net_device *bond_dev,
>  		bond_set_carrier(bond);
>  		eth_hw_addr_random(bond_dev);
>  
> -		if (bond_vlan_used(bond)) {
> +		if (vlan_uses_dev(bond_dev)) {
>  			pr_warning("%s: Warning: clearing HW address of %s while it still has VLANs.\n",
>  				   bond_dev->name, bond_dev->name);
>  			pr_warning("%s: When re-adding slaves, make sure the bond's HW address matches its VLANs'.\n",
> diff --git a/drivers/net/bonding/bonding.h b/drivers/net/bonding/bonding.h
> index 4bf52d5..9c4539e 100644
> --- a/drivers/net/bonding/bonding.h
> +++ b/drivers/net/bonding/bonding.h
> @@ -23,6 +23,7 @@
>  #include <linux/netpoll.h>
>  #include <linux/inetdevice.h>
>  #include <linux/etherdevice.h>
> +#include <linux/if_vlan.h>
>  #include "bond_3ad.h"
>  #include "bond_alb.h"
>  
> @@ -267,9 +268,16 @@ struct bonding {
>  #endif /* CONFIG_DEBUG_FS */
>  };
>  
> +/* use vlan_uses_dev() if under rtnl */
Small nitpick - I don't think this comment is necessary as both calls now reduce
to vlan_uses_dev() and can be used interchangeably, maybe it's better to stick
to bond_vlan_used() just for consistency everywhere.
Anyway, I'm okay with this version as well:

Signed-off-by: Nikolay Aleksandrov <[email-masked]>