vxlan: Read jiffies once when updating FDB 'used' time

Avoid two volatile reads in the data path. Instead, read jiffies once
and only if an FDB entry was found.

Reviewed-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org>
Link: https://patch.msgid.link/20250204145549.1216254-3-idosch@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/vxlan/vxlan_core.c b/drivers/net/vxlan/vxlan_core.c
index 2f2c6606f719153126c3381ac1dec9a714c5a40e..676a93ce3a19726bc85be28ce52b9653314b3c50 100644 (file)
--- a/drivers/net/vxlan/vxlan_core.c
+++ b/drivers/net/vxlan/vxlan_core.c
@@ -434,8 +434,12 @@ static struct vxlan_fdb *vxlan_find_mac(struct vxlan_dev *vxlan,
        struct vxlan_fdb *f;
 
        f = __vxlan_find_mac(vxlan, mac, vni);
-       if (f && READ_ONCE(f->used) != jiffies)
-               WRITE_ONCE(f->used, jiffies);
+       if (f) {
+               unsigned long now = jiffies;
+
+               if (READ_ONCE(f->used) != now)
+                       WRITE_ONCE(f->used, now);
+       }
 
        return f;
 }