netdev - Re: [PATCH v2 net-next 2/3] net: __alloc

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Message-ID: <CANn89iKbV=mmPacj2d0parv9PKyWhKqasU=ufLBvrY90Lbs3Yg@mail.gmail.com>
Date: Sun, 16 Nov 2025 00:48:19 -0800
From: Eric Dumazet <edumazet@...gle.com>
To: Jason Xing <kerneljasonxing@...il.com>
Cc: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, 
	Kuniyuki Iwashima <kuniyu@...gle.com>, netdev@...r.kernel.org, eric.dumazet@...il.com
Subject: Re: [PATCH v2 net-next 2/3] net: __alloc_skb() cleanup

On Sat, Nov 15, 2025 at 5:08 PM Jason Xing <kerneljasonxing@...il.com> wrote:
>
> On Fri, Nov 14, 2025 at 8:12 PM Eric Dumazet <edumazet@...gle.com> wrote:
> >
> > This patch refactors __alloc_skb() to prepare the following one,
> > and does not change functionality.
>
> Well, I think it changes a little bit. Please find below.
>
> >
> > Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> > ---
> >  net/core/skbuff.c | 26 ++++++++++++++++----------
> >  1 file changed, 16 insertions(+), 10 deletions(-)
> >
> > diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> > index 88b5530f9c460d86e12c98e410774444367e0404..c6b065c0a2af265159ee6188469936767a295729 100644
> > --- a/net/core/skbuff.c
> > +++ b/net/core/skbuff.c
> > @@ -646,25 +646,31 @@ static void *kmalloc_reserve(unsigned int *size, gfp_t flags, int node,
> >  struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
> >                             int flags, int node)
> >  {
> > +       struct sk_buff *skb = NULL;
> >         struct kmem_cache *cache;
> > -       struct sk_buff *skb;
> >         bool pfmemalloc;
> >         u8 *data;
> >
> > -       cache = (flags & SKB_ALLOC_FCLONE)
> > -               ? net_hotdata.skbuff_fclone_cache : net_hotdata.skbuff_cache;
> > -
> >         if (sk_memalloc_socks() && (flags & SKB_ALLOC_RX))
> >                 gfp_mask |= __GFP_MEMALLOC;
> >
> > -       /* Get the HEAD */
> > -       if ((flags & (SKB_ALLOC_FCLONE | SKB_ALLOC_NAPI)) == SKB_ALLOC_NAPI &&
> > -           likely(node == NUMA_NO_NODE || node == numa_mem_id()))
> > +       if (flags & SKB_ALLOC_FCLONE) {
> > +               cache = net_hotdata.skbuff_fclone_cache;
> > +               goto fallback;
> > +       }
> > +       cache = net_hotdata.skbuff_cache;
> > +       if (unlikely(node != NUMA_NO_NODE && node != numa_mem_id()))
> > +               goto fallback;
> > +
> > +       if (flags & SKB_ALLOC_NAPI)
> >                 skb = napi_skb_cache_get(true);
>
> IIUC, if it fails to allocate the skb, then...
>
> > -       else
> > +
> > +       if (!skb) {
> > +fallback:
> >                 skb = kmem_cache_alloc_node(cache, gfp_mask & ~GFP_DMA, node);
>
> ...it will retry another way to allocate skb?

Yeah, I guess we can avoid a retry.