net/mlx5e: Protect mod header entry flows list with spinlock

To remove dependency on rtnl lock, extend mod header entry with spinlock
and use it to protect list of flows attached to mod header entry from
concurrent modifications.
Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
Reviewed-by: Jianbo Liu <jianbol@mellanox.com>
Reviewed-by: Roi Dayan <roid@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>

drivers/net/ethernet/mellanox/mlx5/core/en_tc.c

@@ -189,6 +189,8 @@ struct mlx5e_mod_hdr_entry {
 	/* a node of a hash table which keeps all the mod_hdr entries */
 	struct hlist_node mod_hdr_hlist;
 
+	/* protects flows list */
+	spinlock_t flows_lock;
 	/* flows sharing the same mod_hdr entry */
 	struct list_head flows;
 
@@ -358,6 +360,7 @@ static int mlx5e_attach_mod_hdr(struct mlx5e_priv *priv,
 	mh->key.actions = (void *)mh + sizeof(*mh);
 	memcpy(mh->key.actions, key.actions, actions_size);
 	mh->key.num_actions = num_actions;
+	spin_lock_init(&mh->flows_lock);
 	INIT_LIST_HEAD(&mh->flows);
 	refcount_set(&mh->refcnt, 1);
 
@@ -372,7 +375,9 @@ static int mlx5e_attach_mod_hdr(struct mlx5e_priv *priv,
 
 attach_flow:
 	flow->mh = mh;
+	spin_lock(&mh->flows_lock);
 	list_add(&flow->mod_hdr, &mh->flows);
+	spin_unlock(&mh->flows_lock);
 	if (is_eswitch_flow)
 		flow->esw_attr->mod_hdr_id = mh->mod_hdr_id;
 	else
@@ -392,7 +397,9 @@ static void mlx5e_detach_mod_hdr(struct mlx5e_priv *priv,
 	if (!flow->mh)
 		return;
 
+	spin_lock(&flow->mh->flows_lock);
 	list_del(&flow->mod_hdr);
+	spin_unlock(&flow->mh->flows_lock);
 
 	mlx5e_mod_hdr_put(priv, flow->mh);
 	flow->mh = NULL;