On Tue, May 2, 2017 at 6:10 AM, Miroslav Lichvar <mlich...@redhat.com> wrote:
> Since commit b68581778cd0 ("net: Make skb->skb_iif always track
> skb->dev") skbs don't have the original index of the interface which
> received the packet. This information is now needed for a new control
> message related to hardware timestamping.
>
> Instead of adding a new field to skb, we can find the device by the NAPI
> ID if it is available, i.e. CONFIG_NET_RX_BUSY_POLL is enabled and the
> driver is using NAPI. Add dev_get_by_napi_id() and also skb_napi_id() to
> hide the CONFIG_NET_RX_BUSY_POLL ifdef.
>
> CC: Richard Cochran <richardcoch...@gmail.com>
> CC: Willem de Bruijn <will...@google.com>
> Suggested-by: Willem de Bruijn <will...@google.com>
> Signed-off-by: Miroslav Lichvar <mlich...@redhat.com>
> /**
> + * dev_get_by_napi_id - find a device by napi_id
> + * @napi_id: ID of the NAPI struct
> + *
> + * Search for an interface by NAPI ID. Returns %NULL if the device
> + * is not found or a pointer to the device. The device has not had
> + * its reference counter increased so the caller must be careful
> + * about locking. The caller must hold RCU lock.
Instead of a comment, can check with
WARN_ON_ONCE(!rcu_read_lock_held());
> + */
> +
> +struct net_device *dev_get_by_napi_id(unsigned int napi_id)
> +{
> + struct napi_struct *napi;
> +
> + if (napi_id < MIN_NAPI_ID)
> + return NULL;
> +
> + napi = napi_by_id(napi_id);
> + if (napi)
> + return napi->dev;
> +
> + return NULL;
make return NULL the branch expected not taken.
return napi ? napi->dev : NULL;
