Re: [Xen-devel] [PATCH v2 1/1] xen/netback: correctly calculate required slots of skb.

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

> 
> > 
> > 
> > > 
> > > > The code here only 
> > > > increase count for the first time. I thought to initialize the
> > > > count in 
> > > > xen_netbk_count_skb_slots with 1 to avoid this. But thinking of
> > > > the 
> > > > extreme case when the header size is zero(not sure whether this
> > > > case 
> > > > could be true), I increase the count here to keep safe in case
> > > > header 
> > > > size is zero.
> > > 
> > > netfront requires that the first slot always contains some data,
> > > gop_frag_copy will BUG if that's not the case.
> > > 
> 
> 
> In gop_frag_copy, we can not go into the while if the size is 0. Which
> BUG_ON do you mean here?

in gop_frag_copy:
                if (start_new_rx_buffer(npo->copy_off, bytes, *head)) {
                        /*
                         * Netfront requires there to be some data in the head
                         * buffer.
                         */
                        BUG_ON(*head);

Ian



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