Re: [PATCH net-next v2] netdev-genl: Elide napi_id when not present

On Tue, Feb 04, 2025 at 06:41:34AM +0100, Eric Dumazet wrote:

On Mon, Feb 3, 2025 at 8:17 PM Joe Damato [off-list ref] wrote:

quoted

There are at least two cases where napi_id may not present and the
napi_id should be elided:

1. Queues could be created, but napi_enable may not have been called
   yet. In this case, there may be a NAPI but it may not have an ID and
   output of a napi_id should be elided.

2. TX-only NAPIs currently do not have NAPI IDs. If a TX queue happens
   to be linked with a TX-only NAPI, elide the NAPI ID from the netlink
   output as a NAPI ID of 0 is not useful for users.

Signed-off-by: Joe Damato <redacted>
---
 v2:
   - Updated to elide NAPI IDs for RX queues which may have not called
     napi_enable yet.

 rfc: https://lore.kernel.org/lkml/20250128163038.429864-1-jdamato@fastly.com/ (local)
 net/core/netdev-genl.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/net/core/netdev-genl.c b/net/core/netdev-genl.c
index 715f85c6b62e..a97d3b99f6cd 100644
--- a/net/core/netdev-genl.c
+++ b/net/core/netdev-genl.c

@@ -385,9 +385,10 @@ netdev_nl_queue_fill_one(struct sk_buff *rsp, struct net_device *netdev,
        switch (q_type) {
        case NETDEV_QUEUE_TYPE_RX:
                rxq = __netif_get_rx_queue(netdev, q_idx);
-               if (rxq->napi && nla_put_u32(rsp, NETDEV_A_QUEUE_NAPI_ID,
-                                            rxq->napi->napi_id))
-                       goto nla_put_failure;
+               if (rxq->napi && rxq->napi->napi_id >= MIN_NAPI_ID)
+                       if (nla_put_u32(rsp, NETDEV_A_QUEUE_NAPI_ID,
+                                       rxq->napi->napi_id))
+                               goto nla_put_failure;

                binding = rxq->mp_params.mp_priv;
                if (binding &&

@@ -397,9 +398,10 @@ netdev_nl_queue_fill_one(struct sk_buff *rsp, struct net_device *netdev,
                break;
        case NETDEV_QUEUE_TYPE_TX:
                txq = netdev_get_tx_queue(netdev, q_idx);
-               if (txq->napi && nla_put_u32(rsp, NETDEV_A_QUEUE_NAPI_ID,
-                                            txq->napi->napi_id))
-                       goto nla_put_failure;
+               if (txq->napi && txq->napi->napi_id >= MIN_NAPI_ID)
+                       if (nla_put_u32(rsp, NETDEV_A_QUEUE_NAPI_ID,
+                                       txq->napi->napi_id))
+                               goto nla_put_failure;
        }

Hi Joe

This might be time to add helpers, we now have these checks about
MIN_NAPI_ID all around the places.

I'm not sure what the right etiquette is; I was thinking of just
taking the patch you proposed below and submitting it with you as
the author with my Reviewed-by.

Is that OK and if so, are you OK with the commit message?