From: Vlad Buslov <vladbu@mellanox.com>
Date: Fri, 8 Jun 2018 11:49:28 +0300
Subject: net/mlx5e: Extend neigh hash entry with rcu
Patch-mainline: v5.4-rc1
Git-commit: 1216ce9d4a740bed88393177174fef275069a560
References: jsc#SLE-8464

To remove dependency on rtnl lock and to allow unlocked iteration over list
of neigh hash entries, extend nhe with rcu. Change operations on neigh list
to their rcu counterparts and free neigh hash entry with rcu timeout.

Introduce mlx5e_get_next_nhe() helper that is used to iterate over rcu
neigh list with reference to nhe taken.

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>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 drivers/net/ethernet/mellanox/mlx5/core/en_rep.c |   68 ++++++++++++++---------
 drivers/net/ethernet/mellanox/mlx5/core/en_rep.h |    2 
 2 files changed, 46 insertions(+), 24 deletions(-)

--- a/drivers/net/ethernet/mellanox/mlx5/core/en_rep.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_rep.c
@@ -535,28 +535,56 @@ static void mlx5e_rep_neigh_entry_releas
 {
 	if (refcount_dec_and_test(&nhe->refcnt)) {
 		mlx5e_rep_neigh_entry_remove(nhe);
-		kfree(nhe);
+		kfree_rcu(nhe, rcu);
 	}
 }
 
+static struct mlx5e_neigh_hash_entry *
+mlx5e_get_next_nhe(struct mlx5e_rep_priv *rpriv,
+		   struct mlx5e_neigh_hash_entry *nhe)
+{
+	struct mlx5e_neigh_hash_entry *next = NULL;
+
+	rcu_read_lock();
+
+	for (next = nhe ?
+		     list_next_or_null_rcu(&rpriv->neigh_update.neigh_list,
+					   &nhe->neigh_list,
+					   struct mlx5e_neigh_hash_entry,
+					   neigh_list) :
+		     list_first_or_null_rcu(&rpriv->neigh_update.neigh_list,
+					    struct mlx5e_neigh_hash_entry,
+					    neigh_list);
+	     next;
+	     next = list_next_or_null_rcu(&rpriv->neigh_update.neigh_list,
+					  &next->neigh_list,
+					  struct mlx5e_neigh_hash_entry,
+					  neigh_list))
+		if (mlx5e_rep_neigh_entry_hold(next))
+			break;
+
+	rcu_read_unlock();
+
+	if (nhe)
+		mlx5e_rep_neigh_entry_release(nhe);
+
+	return next;
+}
+
 static void mlx5e_rep_neigh_stats_work(struct work_struct *work)
 {
 	struct mlx5e_rep_priv *rpriv = container_of(work, struct mlx5e_rep_priv,
 						    neigh_update.neigh_stats_work.work);
 	struct net_device *netdev = rpriv->netdev;
 	struct mlx5e_priv *priv = netdev_priv(netdev);
-	struct mlx5e_neigh_hash_entry *nhe;
+	struct mlx5e_neigh_hash_entry *nhe = NULL;
 
 	rtnl_lock();
 	if (!list_empty(&rpriv->neigh_update.neigh_list))
 		mlx5e_rep_queue_neigh_stats_work(priv);
 
-	list_for_each_entry(nhe, &rpriv->neigh_update.neigh_list, neigh_list) {
-		if (mlx5e_rep_neigh_entry_hold(nhe)) {
-			mlx5e_tc_update_neigh_used_value(nhe);
-			mlx5e_rep_neigh_entry_release(nhe);
-		}
-	}
+	while ((nhe = mlx5e_get_next_nhe(rpriv, nhe)) != NULL)
+		mlx5e_tc_update_neigh_used_value(nhe);
 
 	rtnl_unlock();
 }
@@ -883,13 +911,9 @@ static int mlx5e_rep_netevent_event(stru
 		m_neigh.family = n->ops->family;
 		memcpy(&m_neigh.dst_ip, n->primary_key, n->tbl->key_len);
 
-		/* We are in atomic context and can't take RTNL mutex, so use
-		 * spin_lock_bh to lookup the neigh table. bh is used since
-		 * netevent can be called from a softirq context.
-		 */
-		spin_lock_bh(&neigh_update->encap_lock);
+		rcu_read_lock();
 		nhe = mlx5e_rep_neigh_entry_lookup(priv, &m_neigh);
-		spin_unlock_bh(&neigh_update->encap_lock);
+		rcu_read_unlock();
 		if (!nhe)
 			return NOTIFY_DONE;
 
@@ -910,19 +934,15 @@ static int mlx5e_rep_netevent_event(stru
 #endif
 			return NOTIFY_DONE;
 
-		/* We are in atomic context and can't take RTNL mutex,
-		 * so use spin_lock_bh to walk the neigh list and look for
-		 * the relevant device. bh is used since netevent can be
-		 * called from a softirq context.
-		 */
-		spin_lock_bh(&neigh_update->encap_lock);
-		list_for_each_entry(nhe, &neigh_update->neigh_list, neigh_list) {
+		rcu_read_lock();
+		list_for_each_entry_rcu(nhe, &neigh_update->neigh_list,
+					neigh_list) {
 			if (p->dev == nhe->m_neigh.dev) {
 				found = true;
 				break;
 			}
 		}
-		spin_unlock_bh(&neigh_update->encap_lock);
+		rcu_read_unlock();
 		if (!found)
 			return NOTIFY_DONE;
 
@@ -995,7 +1015,7 @@ static int mlx5e_rep_neigh_entry_insert(
 	if (err)
 		return err;
 
-	list_add(&nhe->neigh_list, &rpriv->neigh_update.neigh_list);
+	list_add_rcu(&nhe->neigh_list, &rpriv->neigh_update.neigh_list);
 
 	return err;
 }
@@ -1006,7 +1026,7 @@ static void mlx5e_rep_neigh_entry_remove
 
 	spin_lock_bh(&rpriv->neigh_update.encap_lock);
 
-	list_del(&nhe->neigh_list);
+	list_del_rcu(&nhe->neigh_list);
 
 	rhashtable_remove_fast(&rpriv->neigh_update.neigh_ht,
 			       &nhe->rhash_node,
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_rep.h
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_rep.h
@@ -138,6 +138,8 @@ struct mlx5e_neigh_hash_entry {
 	 * 'used' value and avoid neigh deleting by the kernel.
 	 */
 	unsigned long reported_lastuse;
+
+	struct rcu_head rcu;
 };
 
 enum {