netdev - Re: [PATCH net-next v2] netdev-genl: Elide napi

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Message-ID: <Z6JcR5IH8WzH1lP9@LQ3V64L9R2>
Date: Tue, 4 Feb 2025 10:28:23 -0800
From: Joe Damato <jdamato@...tly.com>
To: Eric Dumazet <edumazet@...gle.com>
Cc: netdev@...r.kernel.org, kuba@...nel.org,
	"David S. Miller" <davem@...emloft.net>,
	Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>,
	Amritha Nambiar <amritha.nambiar@...el.com>,
	Mina Almasry <almasrymina@...gle.com>,
	open list <linux-kernel@...r.kernel.org>
Subject: 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 <jdamato@...tly.com> wrote:
> >
> > 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 <jdamato@...tly.com>
> > ---
> >  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/
> >  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?