Re: [PATCH net-next 13/15] vxlan: Do not treat dst cache initialization errors as fatal

[Ido Schimmel <idosch@nvidia.com>]

On Tue, Apr 22, 2025 at 10:49:12AM +0200, Paolo Abeni wrote:
> Note for a possible follow-up: AFAICS, when the allocation fail the
> user-space will have no way to detect it, except for slow down on tx
> using this specific FDB entry, which could be surprising/hard to debug
> or investigate. What about adding an explicit pr_info() message here?

Are you OK with [1]? Using ratelimited() variant as allocation can
be triggered from the data path. Example output:

vxlan: vx1: Failed to initialize dst cache for {00:00:00:0d:02:4f, 10010} -> 198.51.100.20. Tx performance might be degraded

[1]
diff --git a/drivers/net/vxlan/vxlan_core.c b/drivers/net/vxlan/vxlan_core.c
index a56d7239b127..a042d69b3f55 100644
--- a/drivers/net/vxlan/vxlan_core.c
+++ b/drivers/net/vxlan/vxlan_core.c
@@ -569,7 +569,7 @@ static int vxlan_fdb_replace(struct vxlan_fdb *f,
 }
 
 /* Add/update destinations for multicast */
-static int vxlan_fdb_append(struct vxlan_fdb *f,
+static int vxlan_fdb_append(struct vxlan_dev *vxlan, struct vxlan_fdb *f,
 			    union vxlan_addr *ip, __be16 port, __be32 vni,
 			    __u32 ifindex, struct vxlan_rdst **rdp)
 {
@@ -586,7 +586,10 @@ static int vxlan_fdb_append(struct vxlan_fdb *f,
 	/* The driver can work correctly without a dst cache, so do not treat
 	 * dst cache initialization errors as fatal.
 	 */
-	dst_cache_init(&rd->dst_cache, GFP_ATOMIC | __GFP_NOWARN);
+	if (dst_cache_init(&rd->dst_cache, GFP_ATOMIC | __GFP_NOWARN))
+		net_info_ratelimited("%s: Failed to initialize dst cache for {%pM, %u} -> %pISc. Tx performance might be degraded\n",
+				     netdev_name(vxlan->dev), &f->key.eth_addr,
+				     __be32_to_cpu(f->key.vni), &ip->sa);
 
 	rd->remote_ip = *ip;
 	rd->remote_port = port;
@@ -875,7 +878,7 @@ int vxlan_fdb_create(struct vxlan_dev *vxlan,
 	if (nhid)
 		rc = vxlan_fdb_nh_update(vxlan, f, nhid, extack);
 	else
-		rc = vxlan_fdb_append(f, ip, port, vni, ifindex, &rd);
+		rc = vxlan_fdb_append(vxlan, f, ip, port, vni, ifindex, &rd);
 	if (rc < 0)
 		goto errout;
 
@@ -1028,7 +1031,7 @@ static int vxlan_fdb_update_existing(struct vxlan_dev *vxlan,
 	if ((flags & NLM_F_APPEND) &&
 	    (is_multicast_ether_addr(f->key.eth_addr) ||
 	     is_zero_ether_addr(f->key.eth_addr))) {
-		rc = vxlan_fdb_append(f, ip, port, vni, ifindex, &rd);
+		rc = vxlan_fdb_append(vxlan, f, ip, port, vni, ifindex, &rd);
 
 		if (rc < 0)
 			return rc;