Merge branch 'skb_list_cleanups'

Merge branch 'skb_list_cleanups'

David Miller says:

====================
SKB list handling cleanups

This is a preparatory patch series which cleans up various forms of
sloppy SKB list handling, and makes certain semantics explicit.

We are trying to eliminate code that directly accesses the SKB
list and SKB queue head next/prev members in any way.  It is
impossible to convert SKB queue head over the struct list_head
while such code exists.

This patch series does not eliminate all such code, only the simplest
cases.  A latter series will tackle the complicated ones.

A helper is added to make the "skb->next == NULL means not on a list"
rule explicit, and another is added to combine this with list_del().
====================

Signed-off-by: David S. Miller <davem@davemloft.net>