On 2023-08-31 08:58:51 +0200, Eric Dumazet wrote:
> On Thu, Aug 31, 2023 at 1:28 AM Mohamed Khalfella
> <mkhalfella@xxxxxxxxxxxxxxx> wrote:
> > do {
> > struct sk_buff *nskb;
> > skb_frag_t *nskb_frag;
> > @@ -4465,6 +4471,10 @@ struct sk_buff *skb_segment(struct sk_buff *head_skb,
> > (skb_headlen(list_skb) == len || sg)) {
> > BUG_ON(skb_headlen(list_skb) > len);
> >
> > + nskb = skb_clone(list_skb, GFP_ATOMIC);
> > + if (unlikely(!nskb))
> > + goto err;
> > +
>
> This patch is quite complex to review, so I am asking if this part was
> really needed ?
Unfortunately the patch is complex because I try to avoid calling
skb_orphan_frags() in the middle of processing these frags. Otherwise
it would be much harder to implement because as reallocated frags do not
map 1:1 with existing frags as Willem mentioned.
> <1> : You moved here <2> and <3>
<2> was moved here because skb_clone() calls skb_orphan_frags(). By
moving this up we do not need to call skb_orphan_frags() for list_skb
and we can start to use nr_frags and frags without worrying their value
is going to change.
<3> was moved here because <2> was moved here. Fail fast if we can not
clone list_skb.
>
> If this is not strictly needed, please keep the code as is to ease
> code review...
>
> > i = 0;
> > nfrags = skb_shinfo(list_skb)->nr_frags;
> > frag = skb_shinfo(list_skb)->frags;
> > @@ -4483,12 +4493,8 @@ struct sk_buff *skb_segment(struct sk_buff *head_skb,
> > frag++;
> > }
> >
> > - nskb = skb_clone(list_skb, GFP_ATOMIC);
>
> <2>
>
> > list_skb = list_skb->next;
> >
> > - if (unlikely(!nskb))
> > - goto err;
> > -
>
> <3>
>
> > if (unlikely(pskb_trim(nskb, len))) {
> > kfree_skb(nskb);
> > goto err;
> > @@ -4564,12 +4570,16 @@ struct sk_buff *skb_segment(struct sk_buff *head_skb,
> > skb_shinfo(nskb)->flags |= skb_shinfo(head_skb)->flags &
> > SKBFL_SHARED_FRAG;
> >
> > - if (skb_orphan_frags(frag_skb, GFP_ATOMIC) ||
> > - skb_zerocopy_clone(nskb, frag_skb, GFP_ATOMIC))
> > + if (skb_zerocopy_clone(nskb, list_skb, GFP_ATOMIC))
>
> Why using list_skb here instead of frag_skb ?
> Again, I have to look at the whole thing to understand why you did this.
Oops, this is a mistake. It should be frag_skb. Will fix it run the test
one more time and post v3.
