netdev - Re: [PATCH net-next v9 1/3] net: extract napi poll functionality to __napi

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Date:   Wed, 3 Feb 2021 09:00:25 -0800
From:   Alexander Duyck <alexander.duyck@...il.com>
To:     Wei Wang <weiwan@...gle.com>
Cc:     David Miller <davem@...emloft.net>,
        Netdev <netdev@...r.kernel.org>,
        Jakub Kicinski <kuba@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Hannes Frederic Sowa <hannes@...essinduktion.org>,
        Felix Fietkau <nbd@....name>
Subject: Re: [PATCH net-next v9 1/3] net: extract napi poll functionality to __napi_poll()

On Fri, Jan 29, 2021 at 10:20 AM Wei Wang <weiwan@...gle.com> wrote:
>
> From: Felix Fietkau <nbd@....name>
>
> This commit introduces a new function __napi_poll() which does the main
> logic of the existing napi_poll() function, and will be called by other
> functions in later commits.
> This idea and implementation is done by Felix Fietkau <nbd@....name> and
> is proposed as part of the patch to move napi work to work_queue
> context.
> This commit by itself is a code restructure.
>
> Signed-off-by: Felix Fietkau <nbd@....name>
> Signed-off-by: Wei Wang <weiwan@...gle.com>
> ---
>  net/core/dev.c | 35 +++++++++++++++++++++++++----------
>  1 file changed, 25 insertions(+), 10 deletions(-)
>
> diff --git a/net/core/dev.c b/net/core/dev.c
> index 0332f2e8f7da..7d23bff03864 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -6768,15 +6768,10 @@ void __netif_napi_del(struct napi_struct *napi)
>  }
>  EXPORT_SYMBOL(__netif_napi_del);
>
> -static int napi_poll(struct napi_struct *n, struct list_head *repoll)
> +static int __napi_poll(struct napi_struct *n, bool *repoll)
>  {
> -       void *have;
>         int work, weight;
>
> -       list_del_init(&n->poll_list);
> -
> -       have = netpoll_poll_lock(n);
> -
>         weight = n->weight;
>
>         /* This NAPI_STATE_SCHED test is for avoiding a race
> @@ -6796,7 +6791,7 @@ static int napi_poll(struct napi_struct *n, struct list_head *repoll)
>                             n->poll, work, weight);
>
>         if (likely(work < weight))
> -               goto out_unlock;
> +               return work;
>
>         /* Drivers must not modify the NAPI state if they
>          * consume the entire weight.  In such cases this code
> @@ -6805,7 +6800,7 @@ static int napi_poll(struct napi_struct *n, struct list_head *repoll)
>          */
>         if (unlikely(napi_disable_pending(n))) {
>                 napi_complete(n);
> -               goto out_unlock;
> +               return work;
>         }
>
>         /* The NAPI context has more processing work, but busy-polling
> @@ -6818,7 +6813,7 @@ static int napi_poll(struct napi_struct *n, struct list_head *repoll)
>                          */
>                         napi_schedule(n);
>                 }
> -               goto out_unlock;
> +               return work;
>         }
>
>         if (n->gro_bitmask) {
> @@ -6836,9 +6831,29 @@ static int napi_poll(struct napi_struct *n, struct list_head *repoll)
>         if (unlikely(!list_empty(&n->poll_list))) {
>                 pr_warn_once("%s: Budget exhausted after napi rescheduled\n",
>                              n->dev ? n->dev->name : "backlog");
> -               goto out_unlock;
> +               return work;
>         }
>
> +       *repoll = true;
> +
> +       return work;
> +}
> +
> +static int napi_poll(struct napi_struct *n, struct list_head *repoll)
> +{
> +       bool do_repoll = false;
> +       void *have;
> +       int work;
> +
> +       list_del_init(&n->poll_list);
> +
> +       have = netpoll_poll_lock(n);
> +
> +       work = __napi_poll(n, &do_repoll);
> +
> +       if (!do_repoll)
> +               goto out_unlock;
> +
>         list_add_tail(&n->poll_list, repoll);
>
>  out_unlock:

Instead of using the out_unlock label why don't you only do the
list_add_tail if do_repoll is true? It will allow you to drop a few
lines of noise. Otherwise this looks good to me.

Reviewed-by: Alexander Duyck <alexanderduyck@...com>