Subject: [PATCH net-next v5 08/12] virtio_net: Use existing classifier if possible

From: Daniel Jurgens <[email-masked]>
Date: Thu, 16 Oct 2025 00:00:51 -0500

Classifiers can be used by more than one rule. If there is an existing
classifier, use it instead of creating a new one.

Signed-off-by: Daniel Jurgens <[email-masked]>
Reviewed-by: Parav Pandit <[email-masked]>
Reviewed-by: Shahar Shitrit <[email-masked]>
---
v4:
    - Fixed typo in commit message
    - for (int -> for (
---
 drivers/net/virtio_net.c | 42 +++++++++++++++++++++++++++-------------
 1 file changed, 29 insertions(+), 13 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 405ffc015272..e7816e1cc955 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -6806,6 +6806,7 @@ struct virtnet_ethtool_rule {
 /* The classifier struct must be the last field in this struct */
 struct virtnet_classifier {
 	size_t size;
+	refcount_t refcount;
 	u32 id;
 	struct virtio_net_resource_obj_ff_classifier classifier;
 };
@@ -6899,11 +6900,24 @@ 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)
@@ -6911,29 +6925,30 @@ static int setup_classifier(struct virtnet_ff *ff, struct virtnet_classifier *c)
 
 	err = virtio_admin_obj_create(ff->vdev,
 				      VIRTIO_NET_RESOURCE_OBJ_FF_CLASSIFIER,
-				      c->id,
+				      (*c)->id,
 				      VIRTIO_ADMIN_GROUP_TYPE_SELF,
 				      0,
-				      &c->classifier,
-				      c->size);
+				      &(*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_admin_obj_destroy(ff->vdev,
 					 VIRTIO_NET_RESOURCE_OBJ_FF_CLASSIFIER,
 					 c->id,
@@ -6957,7 +6972,7 @@ static void destroy_ethtool_rule(struct virtnet_ff *ff,
 				 0);
 
 	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);
 }
 
@@ -7082,8 +7097,9 @@ validate_classifier_selectors(struct virtnet_ff *ff,
 			      int num_hdrs)
 {
 	struct virtio_net_ff_selector *selector = classifier->selectors;
+	int i;
 
-	for (int i = 0; i < num_hdrs; i++) {
+	for (i = 0; i < num_hdrs; i++) {
 		if (!validate_mask(ff, selector))
 			return -EINVAL;
 
@@ -7137,14 +7153,14 @@ 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 will free the classifier */
-		destroy_classifier(ff, c->id);
+		try_destroy_classifier(ff, c->id);
 		goto err_key;
 	}
 
-- 
2.50.1