vxlan: Convert FDB flushing to RCU

Instead of holding the FDB hash lock when traversing the FDB linked list
during flushing, use RCU and only acquire the lock for entries that need
to be flushed.

Reviewed-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Link: https://patch.msgid.link/20250415121143.345227-11-idosch@nvidia.com
Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

diff --git a/drivers/net/vxlan/vxlan_core.c b/drivers/net/vxlan/vxlan_core.c
index c3511a43ce9984fc7bf0d1960eca270cfec983af..762dde70d9e9cc09f09ce94cceda7d49a9a01ba7 100644 (file)
--- a/drivers/net/vxlan/vxlan_core.c
+++ b/drivers/net/vxlan/vxlan_core.c
@@ -3037,14 +3037,17 @@ static void vxlan_flush(struct vxlan_dev *vxlan,
                        const struct vxlan_fdb_flush_desc *desc)
 {
        bool match_remotes = vxlan_fdb_flush_should_match_remotes(desc);
-       struct hlist_node *n;
        struct vxlan_fdb *f;
 
-       spin_lock_bh(&vxlan->hash_lock);
-       hlist_for_each_entry_safe(f, n, &vxlan->fdb_list, fdb_node) {
+       rcu_read_lock();
+       hlist_for_each_entry_rcu(f, &vxlan->fdb_list, fdb_node) {
                if (!vxlan_fdb_flush_matches(f, vxlan, desc))
                        continue;
 
+               spin_lock_bh(&vxlan->hash_lock);
+               if (hlist_unhashed(&f->fdb_node))
+                       goto unlock;
+
                if (match_remotes) {
                        bool destroy_fdb = false;
 
@@ -3052,12 +3055,14 @@ static void vxlan_flush(struct vxlan_dev *vxlan,
                                                      &destroy_fdb);
 
                        if (!destroy_fdb)
-                               continue;
+                               goto unlock;
                }
 
                vxlan_fdb_destroy(vxlan, f, true, true);
+unlock:
+               spin_unlock_bh(&vxlan->hash_lock);
        }
-       spin_unlock_bh(&vxlan->hash_lock);
+       rcu_read_unlock();
 }
 
 static const struct nla_policy vxlan_del_bulk_policy[NDA_MAX + 1] = {