net/mlx5e: Eswitch, change offloads num_flows type to atomic64

Eswitch implements its own locking by means of state_lock mutex and
multiple fine-grained lock in containing data structures, and is supposed
to not rely on rtnl lock. However, eswitch offloads num_flows type is a
regular long long integer and cannot be modified concurrently. This is an
implicit assumptions that mlx5 tc is serialized (by rtnl lock or any other
means). In order to remove implicit dependency on rtnl lock, change
num_flows type to atomic64 to allow concurrent modifications.

Signed-off-by: Vlad Buslov <[email protected]>
Reviewed-by: Jianbo Liu <[email protected]>
Reviewed-by: Roi Dayan <[email protected]>
Signed-off-by: Saeed Mahameed <[email protected]>

Author: w1ldptr

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

@@ -1933,6 +1933,7 @@ int mlx5_eswitch_init(struct mlx5_core_dev *dev)
 
 	hash_init(esw->offloads.encap_tbl);
 	hash_init(esw->offloads.mod_hdr_tbl);
+	atomic64_set(&esw->offloads.num_flows, 0);
 	mutex_init(&esw->state_lock);
 
 	mlx5_esw_for_all_vports(esw, i, vport) {

drivers/net/ethernet/mellanox/mlx5/core/eswitch.h

@@ -35,6 +35,7 @@
 
 #include <linux/if_ether.h>
 #include <linux/if_link.h>
+#include <linux/atomic.h>
 #include <net/devlink.h>
 #include <linux/mlx5/device.h>
 #include <linux/mlx5/eswitch.h>
@@ -179,7 +180,7 @@ struct mlx5_esw_offload {
 	struct mutex termtbl_mutex; /* protects termtbl hash */
 	const struct mlx5_eswitch_rep_ops *rep_ops[NUM_REP_TYPES];
 	u8 inline_mode;
-	u64 num_flows;
+	atomic64_t num_flows;
 	enum devlink_eswitch_encap_mode encap;
 };
 

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

@@ -233,7 +233,7 @@ mlx5_eswitch_add_offloaded_rule(struct mlx5_eswitch *esw,
 	if (IS_ERR(rule))
 		goto err_add_rule;
 	else
-		esw->offloads.num_flows++;
+		atomic64_inc(&esw->offloads.num_flows);
 
 	return rule;
 
@@ -298,7 +298,7 @@ mlx5_eswitch_add_fwd_rule(struct mlx5_eswitch *esw,
 	if (IS_ERR(rule))
 		goto add_err;
 
-	esw->offloads.num_flows++;
+	atomic64_inc(&esw->offloads.num_flows);
 
 	return rule;
 add_err:
@@ -326,7 +326,7 @@ __mlx5_eswitch_del_rule(struct mlx5_eswitch *esw,
 			mlx5_eswitch_termtbl_put(esw, attr->dests[i].termtbl);
 	}
 
-	esw->offloads.num_flows--;
+	atomic64_dec(&esw->offloads.num_flows);
 
 	if (fwd_rule)  {
 		esw_put_prio_table(esw, attr->chain, attr->prio, 1);
@@ -2349,7 +2349,7 @@ int mlx5_devlink_eswitch_inline_mode_set(struct devlink *devlink, u8 mode,
 		break;
 	}
 
-	if (esw->offloads.num_flows > 0) {
+	if (atomic64_read(&esw->offloads.num_flows) > 0) {
 		NL_SET_ERR_MSG_MOD(extack,
 				   "Can't set inline mode when flows are configured");
 		return -EOPNOTSUPP;
@@ -2459,7 +2459,7 @@ int mlx5_devlink_eswitch_encap_mode_set(struct devlink *devlink,
 	if (esw->offloads.encap == encap)
 		return 0;
 
-	if (esw->offloads.num_flows > 0) {
+	if (atomic64_read(&esw->offloads.num_flows) > 0) {
 		NL_SET_ERR_MSG_MOD(extack,
 				   "Can't set encapsulation when flows are configured");
 		return -EOPNOTSUPP;