[ovs-dev] [PATCH] datapath: Refactor get_dp() function, add get_dp_rcu()

[Pravin Shelar]

On Tue, Jul 15, 2014 at 2:56 PM, Andy Zhou <azhou at nicira.com> wrote:
> The added get_dp_rcu() requires its caller to hold rcu lock.
> get_dp() now requires caller to hold ovs lock.
>
> Sepearate APIs makes it clear on the intended use and the requirements
> of its caller.
>
> Signed-off-by: Andy Zhou <azhou at nicira.com>
> ---
>  datapath/datapath.c | 23 +++++++++++++++++------
>  1 file changed, 17 insertions(+), 6 deletions(-)
>
> diff --git a/datapath/datapath.c b/datapath/datapath.c
> index 065356f..56f5b72 100644
> --- a/datapath/datapath.c
> +++ b/datapath/datapath.c
> @@ -140,19 +140,30 @@ static int queue_gso_packets(struct datapath *dp, struct sk_buff *,
>  static int queue_userspace_packet(struct datapath *dp, struct sk_buff *,
>                                   const struct dp_upcall_info *);
>
> -/* Must be called with rcu_read_lock or ovs_mutex. */
> -static struct datapath *get_dp(struct net *net, int dp_ifindex)
> +/* Must be called with rcu_read_lock. */
> +static struct datapath *get_dp_rcu(struct net *net, int dp_ifindex)
>  {
> +       struct net_device *dev = dev_get_by_index_rcu(net, dp_ifindex);
>         struct datapath *dp = NULL;
> -       struct net_device *dev;
>
> -       rcu_read_lock();
> -       dev = dev_get_by_index_rcu(net, dp_ifindex);
>         if (dev) {
>                 struct vport *vport = ovs_internal_dev_get_vport(dev);
>                 if (vport)
>                         dp = vport->dp;
>         }
> +
> +       return dp;
> +}
> +
> +/* The caller must hold ovs_mutex to keep the returned dp pointer valid. */
> +static struct datapath *get_dp(struct net *net, int dp_ifindex)
> +{
> +       struct datapath *dp = NULL;
> +
This assignment is not required.

> +       ASSERT_OVSL();
> +
There are call sites for get_dp() holding only rcu-read-lock where
this assert fails.


> +       rcu_read_lock();
> +       dp = get_dp_rcu(net, dp_ifindex);
>         rcu_read_unlock();
>
>         return dp;
> @@ -595,7 +606,7 @@ static int ovs_packet_cmd_execute(struct sk_buff *skb, struct genl_info *info)
>         packet->mark = flow->key.phy.skb_mark;
>
>         rcu_read_lock();
> -       dp = get_dp(sock_net(skb->sk), ovs_header->dp_ifindex);
> +       dp = get_dp_rcu(sock_net(skb->sk), ovs_header->dp_ifindex);
>         err = -ENODEV;
>         if (!dp)
>                 goto err_unlock;
> --
> 1.9.1
>
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