Commit 481ff57a authored by Jiri Pirko's avatar Jiri Pirko Committed by David S. Miller
Browse files

mlxsw: spectrum: Avoid copying sample values and use RCU pointer direcly instead 



Currently, only the psample_group is accessed using RCU on RX path.
However, it is possible (unlikely) that other sample values get change
during RX processing. Fix this by having the port->sample struct
accessed as RCU pointer, containing all sample values including
psample_group pointer. That avoids extra alloc per-port, copying the
values and the race condition described above.

Signed-off-by: default avatarJiri Pirko <jiri@mellanox.com>
Signed-off-by: default avatarIdo Schimmel <idosch@mellanox.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent dd0fbc89

drivers/net/ethernet/mellanox/mlxsw/spectrum.c

+6 −24
Original line number Diff line number Diff line
@@ -3527,13 +3527,6 @@ static int mlxsw_sp_port_create(struct mlxsw_sp *mlxsw_sp, u8 local_port, 
		goto err_alloc_stats;

	}



	mlxsw_sp_port->sample = kzalloc(sizeof(*mlxsw_sp_port->sample),

					GFP_KERNEL);

	if (!mlxsw_sp_port->sample) {

		err = -ENOMEM;

		goto err_alloc_sample;

	}



	INIT_DELAYED_WORK(&mlxsw_sp_port->periodic_hw_stats.update_dw,

			  &update_stats_cache);
@@ -3720,8 +3713,6 @@ err_dev_addr_init: 
err_port_swid_set:

	mlxsw_sp_port_module_unmap(mlxsw_sp_port);

err_port_module_map:

	kfree(mlxsw_sp_port->sample);

err_alloc_sample:

	free_percpu(mlxsw_sp_port->pcpu_stats);

err_alloc_stats:

	free_netdev(dev);
@@ -3749,7 +3740,6 @@ static void mlxsw_sp_port_remove(struct mlxsw_sp *mlxsw_sp, u8 local_port) 
	mlxsw_sp_port_tc_mc_mode_set(mlxsw_sp_port, false);

	mlxsw_sp_port_swid_set(mlxsw_sp_port, MLXSW_PORT_SWID_DISABLED_PORT);

	mlxsw_sp_port_module_unmap(mlxsw_sp_port);

	kfree(mlxsw_sp_port->sample);

	free_percpu(mlxsw_sp_port->pcpu_stats);

	WARN_ON_ONCE(!list_empty(&mlxsw_sp_port->vlans_list));

	free_netdev(mlxsw_sp_port->dev);
@@ -4236,7 +4226,7 @@ static void mlxsw_sp_rx_listener_sample_func(struct sk_buff *skb, u8 local_port, 
{

	struct mlxsw_sp *mlxsw_sp = priv;

	struct mlxsw_sp_port *mlxsw_sp_port = mlxsw_sp->ports[local_port];

	struct psample_group *psample_group;

	struct mlxsw_sp_port_sample *sample;

	u32 size;



	if (unlikely(!mlxsw_sp_port)) {
@@ -4244,22 +4234,14 @@ static void mlxsw_sp_rx_listener_sample_func(struct sk_buff *skb, u8 local_port, 
				     local_port);

		goto out;

	}

	if (unlikely(!mlxsw_sp_port->sample)) {

		dev_warn_ratelimited(mlxsw_sp->bus_info->dev, "Port %d: sample skb received on unsupported port\n",

				     local_port);

		goto out;

	}



	size = mlxsw_sp_port->sample->truncate ?

		  mlxsw_sp_port->sample->trunc_size : skb->len;



	rcu_read_lock();

	psample_group = rcu_dereference(mlxsw_sp_port->sample->psample_group);

	if (!psample_group)

	sample = rcu_dereference(mlxsw_sp_port->sample);

	if (!sample)

		goto out_unlock;

	psample_sample_packet(psample_group, skb, size,

			      mlxsw_sp_port->dev->ifindex, 0,

			      mlxsw_sp_port->sample->rate);

	size = sample->truncate ? sample->trunc_size : skb->len;

	psample_sample_packet(sample->psample_group, skb, size,

			      mlxsw_sp_port->dev->ifindex, 0, sample->rate);

out_unlock:

	rcu_read_unlock();

out:

drivers/net/ethernet/mellanox/mlxsw/spectrum.h

+2 −2
Original line number Diff line number Diff line
@@ -192,7 +192,7 @@ struct mlxsw_sp_port_pcpu_stats { 
};



struct mlxsw_sp_port_sample {

	struct psample_group __rcu *psample_group;

	struct psample_group *psample_group;

	u32 trunc_size;

	u32 rate;

	bool truncate;
@@ -262,7 +262,7 @@ struct mlxsw_sp_port { 
		struct mlxsw_sp_port_xstats xstats;

		struct delayed_work update_dw;

	} periodic_hw_stats;

	struct mlxsw_sp_port_sample *sample;

	struct mlxsw_sp_port_sample __rcu *sample;

	struct list_head vlans_list;

	struct mlxsw_sp_port_vlan *default_vlan;

	struct mlxsw_sp_qdisc_state *qdisc;

drivers/net/ethernet/mellanox/mlxsw/spectrum_matchall.c

+6 −11
Original line number Diff line number Diff line
@@ -29,6 +29,7 @@ struct mlxsw_sp_mall_entry { 
		struct mlxsw_sp_mall_mirror_entry mirror;

		struct mlxsw_sp_port_sample sample;

	};

	struct rcu_head rcu;

};



static struct mlxsw_sp_mall_entry *
@@ -90,17 +91,11 @@ mlxsw_sp_mall_port_sample_add(struct mlxsw_sp_port *mlxsw_sp_port, 
{

	int err;



	if (!mlxsw_sp_port->sample)

		return -EOPNOTSUPP;

	if (rtnl_dereference(mlxsw_sp_port->sample->psample_group)) {

	if (rtnl_dereference(mlxsw_sp_port->sample)) {

		netdev_err(mlxsw_sp_port->dev, "sample already active\n");

		return -EEXIST;

	}

	rcu_assign_pointer(mlxsw_sp_port->sample->psample_group,

			   mall_entry->sample.psample_group);

	mlxsw_sp_port->sample->truncate = mall_entry->sample.truncate;

	mlxsw_sp_port->sample->trunc_size = mall_entry->sample.trunc_size;

	mlxsw_sp_port->sample->rate = mall_entry->sample.rate;

	rcu_assign_pointer(mlxsw_sp_port->sample, &mall_entry->sample);



	err = mlxsw_sp_mall_port_sample_set(mlxsw_sp_port, true,

					    mall_entry->sample.rate);
@@ -109,7 +104,7 @@ mlxsw_sp_mall_port_sample_add(struct mlxsw_sp_port *mlxsw_sp_port, 
	return 0;



err_port_sample_set:

	RCU_INIT_POINTER(mlxsw_sp_port->sample->psample_group, NULL);

	RCU_INIT_POINTER(mlxsw_sp_port->sample, NULL);

	return err;

}
@@ -120,7 +115,7 @@ mlxsw_sp_mall_port_sample_del(struct mlxsw_sp_port *mlxsw_sp_port) 
		return;



	mlxsw_sp_mall_port_sample_set(mlxsw_sp_port, false, 1);

	RCU_INIT_POINTER(mlxsw_sp_port->sample->psample_group, NULL);

	RCU_INIT_POINTER(mlxsw_sp_port->sample, NULL);

}



static int
@@ -221,5 +216,5 @@ void mlxsw_sp_mall_destroy(struct mlxsw_sp_port *mlxsw_sp_port, 
	mlxsw_sp_mall_port_rule_del(mlxsw_sp_port, mall_entry);



	list_del(&mall_entry->list);

	kfree(mall_entry);

	kfree_rcu(mall_entry, rcu); /* sample RX packets may be in-flight */

}

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