On Sat, Jan 05, 2013 at 06:16:31PM -0800, Eric Dumazet wrote:
> On Sat, 2013-01-05 at 17:51 -0800, Eric Dumazet wrote:
> > On Sat, 2013-01-05 at 17:40 -0800, Eric Dumazet wrote:
> > > On Sun, 2013-01-06 at 02:30 +0100, Willy Tarreau wrote:
> > > 
> > > > Ah interesting because these were some of the mm patches that I had
> > > > tried to revert.
> > > 
> > > Hmm, or we should fix __skb_splice_bits()
> > > 
> > > I'll send a patch.
> > > 
> > 
> > Could you try the following ?
> 
> Or more exactly...

The first one did not change a iota unfortunately. I'm about to
spot the commit causing the loopback regression. It's a few patches
before the first one you pointed. It's almost finished and I test
your patch below immediately after.

Thanks,
Willy

> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index 3ab989b..01f222c 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -1736,11 +1736,8 @@ static bool __splice_segment(struct page *page, 
> unsigned int poff,
>               return false;
>       }
>  
> -     /* ignore any bits we already processed */
> -     if (*off) {
> -             __segment_seek(&page, &poff, &plen, *off);
> -             *off = 0;
> -     }
> +     __segment_seek(&page, &poff, &plen, *off);
> +     *off = 0;
>  
>       do {
>               unsigned int flen = min(*len, plen);
> @@ -1768,14 +1765,15 @@ static bool __skb_splice_bits(struct sk_buff *skb, 
> struct pipe_inode_info *pipe,
>                             struct splice_pipe_desc *spd, struct sock *sk)
>  {
>       int seg;
> +     struct page *page = virt_to_page(skb->data);
> +     unsigned int poff = skb->data - (unsigned char *)page_address(page);
>  
>       /* map the linear part :
>        * If skb->head_frag is set, this 'linear' part is backed by a
>        * fragment, and if the head is not shared with any clones then
>        * we can avoid a copy since we own the head portion of this page.
>        */
> -     if (__splice_segment(virt_to_page(skb->data),
> -                          (unsigned long) skb->data & (PAGE_SIZE - 1),
> +     if (__splice_segment(page, poff,
>                            skb_headlen(skb),
>                            offset, len, skb, spd,
>                            skb_head_is_locked(skb),
> 
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