netdev - Re: [PATCH net] net: bridge: vlan: Add a schedule point during VLAN processing

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Date:   Thu, 30 Apr 2020 23:25:40 +0300
From:   Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
To:     Ido Schimmel <idosch@...sch.org>, netdev@...r.kernel.org,
        bridge@...ts.linux-foundation.org
Cc:     davem@...emloft.net, kuba@...nel.org, roopa@...ulusnetworks.com,
        s.priebe@...fihost.ag, mlxsw@...lanox.com,
        Ido Schimmel <idosch@...lanox.com>
Subject: Re: [PATCH net] net: bridge: vlan: Add a schedule point during VLAN
 processing

On 30/04/2020 22:38, Ido Schimmel wrote:
> From: Ido Schimmel <idosch@...lanox.com>
> 
> User space can request to delete a range of VLANs from a bridge slave in
> one netlink request. For each deleted VLAN the FDB needs to be traversed
> in order to flush all the affected entries.
> 
> If a large range of VLANs is deleted and the number of FDB entries is
> large or the FDB lock is contented, it is possible for the kernel to
> loop through the deleted VLANs for a long time. In case preemption is
> disabled, this can result in a soft lockup.
> 
> Fix this by adding a schedule point after each VLAN is deleted to yield
> the CPU, if needed. This is safe because the VLANs are traversed in
> process context.
> 
> Fixes: bdced7ef7838 ("bridge: support for multiple vlans and vlan ranges in setlink and dellink requests")
> Signed-off-by: Ido Schimmel <idosch@...lanox.com>
> Reported-by: Stefan Priebe - Profihost AG <s.priebe@...fihost.ag>
> Tested-by: Stefan Priebe - Profihost AG <s.priebe@...fihost.ag>
> ---
>  net/bridge/br_netlink.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
> index 43dab4066f91..a0f5dbee8f9c 100644
> --- a/net/bridge/br_netlink.c
> +++ b/net/bridge/br_netlink.c
> @@ -612,6 +612,7 @@ int br_process_vlan_info(struct net_bridge *br,
>  					       v - 1, rtm_cmd);
>  				v_change_start = 0;
>  			}
> +			cond_resched();
>  		}
>  		/* v_change_start is set only if the last/whole range changed */
>  		if (v_change_start)
> 

Looks good, thanks!
Acked-by: Nikolay Aleksandrov <nikolay@...ulusnetworks.com>