On Fri, Jan 15, 2021 at 1:36 AM Xin Long <lucien.xin@xxxxxxxxx> wrote:
>
> After commit 89319d3801d1 ("net: Add frag_list support to skb_segment"),
> it goes to process frag_list when !hsize in skb_segment(). However, when
> using skb frag_list, sg normally should not be set. In this case, hsize
> will be set with len right before !hsize check, then it won't go to
> frag_list processing code.
>
> So the right thing to do is move the hsize check to the else block, so
> that it won't affect the !hsize check for frag_list processing.
>
> v1->v2:
> - change to do "hsize <= 0" check instead of "!hsize", and also move
> "hsize < 0" into else block, to save some cycles, as Alex suggested.
>
> Signed-off-by: Xin Long <lucien.xin@xxxxxxxxx>
Looks good to me.
Reviewed-by: Alexander Duyck <alexanderduyck@xxxxxx>
> ---
> net/core/skbuff.c | 11 ++++++-----
> 1 file changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index 6039069..e835193 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -3894,12 +3894,8 @@ struct sk_buff *skb_segment(struct sk_buff *head_skb,
> }
>
> hsize = skb_headlen(head_skb) - offset;
> - if (hsize < 0)
> - hsize = 0;
> - if (hsize > len || !sg)
> - hsize = len;
>
> - if (!hsize && i >= nfrags && skb_headlen(list_skb) &&
> + if (hsize <= 0 && i >= nfrags && skb_headlen(list_skb) &&
> (skb_headlen(list_skb) == len || sg)) {
> BUG_ON(skb_headlen(list_skb) > len);
>
> @@ -3942,6 +3938,11 @@ struct sk_buff *skb_segment(struct sk_buff *head_skb,
> skb_release_head_state(nskb);
> __skb_push(nskb, doffset);
> } else {
> + if (hsize > len || !sg)
> + hsize = len;
> + else if (hsize < 0)
> + hsize = 0;
> +
> nskb = __alloc_skb(hsize + doffset + headroom,
> GFP_ATOMIC, skb_alloc_rx_flag(head_skb),
> NUMA_NO_NODE);
> --
> 2.1.0
>
