Merge branch 'skb-coalescing-page_pool'

Liang Chen says:

====================
skbuff: Optimize SKB coalescing for page pool

The combination of the following condition was excluded from skb coalescing:

from->pp_recycle = 1
from->cloned = 1
to->pp_recycle = 1

With page pool in use, this combination can be quite common(ex.
NetworkMananger may lead to the additional packet_type being registered,
thus the cloning). In scenarios with a higher number of small packets, it
can significantly affect the success rate of coalescing.

This patchset aims to optimize this scenario and enable coalescing of this
particular combination. That also involves supporting multiple users
referencing the same fragment of a pp page to accomondate the need to
increment the "from" SKB page's pp page reference count.

Changes from v10:
- re-number patches to 1/3, 2/3, 3/3

Changes from v9:
- patch 1 was already applied
- imporve description for patch 2
- make sure skb_pp_frag_ref only work for pp aware skbs
====================

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