Re: Is: SKB_MAX_LEN bites again. Was: Re: bug disabling guest interface

Wei Liu
Sun, 10 Mar 2013 19:18:38 -0000

On Sat, Mar 09, 2013 at 02:57:16AM +0000, Ian Campbell
wrote:
> > > - change MAX_SKB_FRAGS to 19 to accommodate all guests
>
> Changing MAX_SKB_FRAGS is *not* an option upstream. This might be a
> useful local hack but we need to drop the idea as a long term fix.
>
> > Ugh. The negotiations between host and guest is probably the best
> > choice. The issues you are going to hit are that you might need
> > to redo the skbs to match what the frontend''s max is.
>
> IMHO the right fix is for netback to coalesce as it copies from the
> frontend if it needs to do so, it is copying anyway so it should be
> cheap enough. I thought we had discussed this and someone was working on
> implementing it. If not Annie then perhaps it was Matt or Siva (both now
> CC''d)
>

As a short term fix, can we use skb_linearize() if skb->nr_frags
>MAX_SKB_FRAGS?


Wei.