Re: [PATCH net-next v3 07/11] virtio_net: Use existing classifier if possible

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Sep 23, 2025 at 09:19:16AM -0500, Daniel Jurgens wrote:
> Classifiers can be used by more than one rule. If there is an exisitng

existing

> classifier, use it instead of creating a new one.
> 
> Signed-off-by: Daniel Jurgens <danielj@nvidia.com>
> Reviewed-by: Parav Pandit <parav@nvidia.com>
> Reviewed-by: Shahar Shitrit <shshitrit@nvidia.com>
> ---
>  drivers/net/virtio_net/virtio_net_ff.c | 39 ++++++++++++++++++--------
>  1 file changed, 27 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/net/virtio_net/virtio_net_ff.c b/drivers/net/virtio_net/virtio_net_ff.c
> index e3c34bfd1d55..30c5ded57ab5 100644
> --- a/drivers/net/virtio_net/virtio_net_ff.c
> +++ b/drivers/net/virtio_net/virtio_net_ff.c
> @@ -17,6 +17,7 @@ struct virtnet_ethtool_rule {
>  /* New fields must be added before the classifier struct */
>  struct virtnet_classifier {
>  	size_t size;
> +	refcount_t refcount;
>  	u32 id;
>  	struct virtio_net_resource_obj_ff_classifier classifier;
>  };
> @@ -105,11 +106,24 @@ static bool validate_mask(const struct virtnet_ff *ff,
>  	return false;
>  }
>  
> -static int setup_classifier(struct virtnet_ff *ff, struct virtnet_classifier *c)
> +static int setup_classifier(struct virtnet_ff *ff,
> +			    struct virtnet_classifier **c)
>  {
> +	struct virtnet_classifier *tmp;
> +	unsigned long i;
>  	int err;
>  
> -	err = xa_alloc(&ff->classifiers, &c->id, c,
> +	xa_for_each(&ff->classifiers, i, tmp) {
> +		if ((*c)->size == tmp->size &&
> +		    !memcmp(&tmp->classifier, &(*c)->classifier, tmp->size)) {
> +			refcount_inc(&tmp->refcount);
> +			kfree(*c);
> +			*c = tmp;
> +			goto out;
> +		}
> +	}
> +
> +	err = xa_alloc(&ff->classifiers, &(*c)->id, *c,
>  		       XA_LIMIT(0, le32_to_cpu(ff->ff_caps->classifiers_limit) - 1),
>  		       GFP_KERNEL);
>  	if (err)
> @@ -117,27 +131,28 @@ static int setup_classifier(struct virtnet_ff *ff, struct virtnet_classifier *c)
>  
>  	err = virtio_device_object_create(ff->vdev,
>  					  VIRTIO_NET_RESOURCE_OBJ_FF_CLASSIFIER,
> -					  c->id,
> -					  &c->classifier,
> -					  c->size);
> +					  (*c)->id,
> +					  &(*c)->classifier,
> +					  (*c)->size);
>  	if (err)
>  		goto err_xarray;
>  
> +	refcount_set(&(*c)->refcount, 1);
> +out:
>  	return 0;
>  
>  err_xarray:
> -	xa_erase(&ff->classifiers, c->id);
> +	xa_erase(&ff->classifiers, (*c)->id);
>  
>  	return err;
>  }
>  
> -static void destroy_classifier(struct virtnet_ff *ff,
> -			       u32 classifier_id)
> +static void try_destroy_classifier(struct virtnet_ff *ff, u32 classifier_id)
>  {
>  	struct virtnet_classifier *c;
>  
>  	c = xa_load(&ff->classifiers, classifier_id);
> -	if (c) {
> +	if (c && refcount_dec_and_test(&c->refcount)) {
>  		virtio_device_object_destroy(ff->vdev,
>  					     VIRTIO_NET_RESOURCE_OBJ_FF_CLASSIFIER,
>  					     c->id);
> @@ -157,7 +172,7 @@ static void destroy_ethtool_rule(struct virtnet_ff *ff,
>  				     eth_rule->flow_spec.location);
>  
>  	xa_erase(&ff->ethtool.rules, eth_rule->flow_spec.location);
> -	destroy_classifier(ff, eth_rule->classifier_id);
> +	try_destroy_classifier(ff, eth_rule->classifier_id);
>  	kfree(eth_rule);
>  }
>  
> @@ -340,13 +355,13 @@ static int build_and_insert(struct virtnet_ff *ff,
>  	if (err)
>  		goto err_key;
>  
> -	err = setup_classifier(ff, c);
> +	err = setup_classifier(ff, &c);
>  	if (err)
>  		goto err_classifier;
>  
>  	err = insert_rule(ff, eth_rule, c->id, key, key_size);
>  	if (err) {
> -		destroy_classifier(ff, c->id);
> +		try_destroy_classifier(ff, c->id);
>  		goto err_key;
>  	}
>  
> -- 
> 2.45.0