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

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Date:   Wed, 3 Feb 2021 09:57:23 -0800
From:   Wei Wang <weiwan@...gle.com>
To:     Alexander Duyck <alexander.duyck@...il.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 Wed, Feb 3, 2021 at 9:00 AM Alexander Duyck
<alexander.duyck@...il.com> wrote:
>
> 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.
>
Ack.

> Reviewed-by: Alexander Duyck <alexanderduyck@...com>
Thanks for the review.