Merge branch 'simplify-do_redirect'

Björn Töpel says:

====================
This series aims to simplify the XDP maps and
xdp_do_redirect_map()/xdp_do_flush_map(), and to crank out some more
performance from XDP_REDIRECT scenarios.

The first part of the series simplifies all XDP_REDIRECT capable maps,
so that __XXX_flush_map() does not require the map parameter, by
moving the flush list from the map to global scope.

This results in that the map_to_flush member can be removed from
struct bpf_redirect_info, and its corresponding logic.

Simpler code, and more performance due to that checks/code per-packet
is moved to flush.

Pre-series performance:
  $ sudo taskset -c 22 ./xdpsock -i enp134s0f0 -q 20 -n 1 -r -z

   sock0@enp134s0f0:20 rxdrop xdp-drv
                  pps         pkts        1.00
  rx              20,797,350  230,942,399
  tx              0           0

  $ sudo ./xdp_redirect_cpu --dev enp134s0f0 --cpu 22 xdp_cpu_map0

  Running XDP/eBPF prog_name:xdp_cpu_map5_lb_hash_ip_pairs
  XDP-cpumap      CPU:to  pps            drop-pps    extra-info
  XDP-RX          20      7723038        0           0
  XDP-RX          total   7723038        0
  cpumap_kthread  total   0              0           0
  redirect_err    total   0              0
  xdp_exception   total   0              0

Post-series performance:
  $ sudo taskset -c 22 ./xdpsock -i enp134s0f0 -q 20 -n 1 -r -z

   sock0@enp134s0f0:20 rxdrop xdp-drv
                  pps         pkts        1.00
  rx              21,524,979  86,835,327
  tx              0           0

  $ sudo ./xdp_redirect_cpu --dev enp134s0f0 --cpu 22 xdp_cpu_map0

  Running XDP/eBPF prog_name:xdp_cpu_map5_lb_hash_ip_pairs
  XDP-cpumap      CPU:to  pps            drop-pps    extra-info
  XDP-RX          20      7840124        0           0
  XDP-RX          total   7840124        0
  cpumap_kthread  total   0              0           0
  redirect_err    total   0              0
  xdp_exception   total   0              0

Results: +3.5% and +1.5% for the ubenchmarks.

v1->v2 [1]:
  * Removed 'unused-variable' compiler warning (Jakub)

[1] https://lore.kernel.org/bpf/20191218105400.2895-1-bjorn.topel@gmail.com/
====================

Signed-off-by: Alexei Starovoitov <ast@kernel.org>