On Mon, Aug 17, 2020 at 04:34:07PM +0300, Maxim Mikityanskiy wrote:
> The legacy ethtool userspace tool shows an error when no features could
> be changed. It's useful to have a netlink reply to be able to show this
> error when __netdev_update_features wasn't called, for example:
>
> 1. ethtool -k eth0
> large-receive-offload: off
> 2. ethtool -K eth0 rx-fcs on
> 3. ethtool -K eth0 lro on
> Could not change any device features
> rx-lro: off [requested on]
> 4. ethtool -K eth0 lro on
> # The output should be the same, but without this patch the kernel
> # doesn't send the reply, and ethtool is unable to detect the error.
>
> This commit makes ethtool-netlink always return a reply when requested,
> and it still avoids unnecessary calls to __netdev_update_features if the
> wanted features haven't changed.
>
> Fixes: 0980bfcd6954 ("ethtool: set netdev features with FEATURES_SET request")
> Signed-off-by: Maxim Mikityanskiy <maxi...@mellanox.com>
Reviewed-by: Michal Kubecek <mkube...@suse.cz>
> ---
> net/ethtool/features.c | 11 ++++-------
> 1 file changed, 4 insertions(+), 7 deletions(-)
>
> diff --git a/net/ethtool/features.c b/net/ethtool/features.c
> index 6b288bfd7678..495635f152ba 100644
> --- a/net/ethtool/features.c
> +++ b/net/ethtool/features.c
> @@ -268,14 +268,11 @@ int ethnl_set_features(struct sk_buff *skb, struct
> genl_info *info)
> bitmap_and(req_wanted, req_wanted, req_mask, NETDEV_FEATURE_COUNT);
> bitmap_andnot(new_wanted, old_wanted, req_mask, NETDEV_FEATURE_COUNT);
> bitmap_or(req_wanted, new_wanted, req_wanted, NETDEV_FEATURE_COUNT);
> - if (bitmap_equal(req_wanted, old_wanted, NETDEV_FEATURE_COUNT)) {
> - ret = 0;
> - goto out_rtnl;
> + if (!bitmap_equal(req_wanted, old_wanted, NETDEV_FEATURE_COUNT)) {
> + dev->wanted_features &= ~dev->hw_features;
> + dev->wanted_features |= ethnl_bitmap_to_features(req_wanted) &
> dev->hw_features;
> + __netdev_update_features(dev);
> }
> -
> - dev->wanted_features &= ~dev->hw_features;
> - dev->wanted_features |= ethnl_bitmap_to_features(req_wanted) &
> dev->hw_features;
> - __netdev_update_features(dev);
> ethnl_features_to_bitmap(new_active, dev->features);
> mod = !bitmap_equal(old_active, new_active, NETDEV_FEATURE_COUNT);
We could also move these last two lines to the branch where
__netdev_update_features() is actually called and replace them with
bitmap_copy(new_active, old_active, NETDEV_FEATURE_COUNT);
mod = false;
otherwise. But it's probably not worth complicating the code.
Michal
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