[PATCH net-next v4 0/3] udp msg_zerocopy

[Willem de Bruijn <willemdebruijn.kernel@gmail.com>]

From: Willem de Bruijn <willemb@google.com>

Enable MSG_ZEROCOPY for udp sockets

Patch 1/3 is the main patch, a rework of RFC patch
  http://patchwork.ozlabs.org/patch/899630/
  more details in the patch commit message

Patch 2/3 is an optimization to remove a branch from the UDP hot path
  and refcount_inc/refcount_dec_and_test pair when zerocopy is used.
  This used to be included in the first patch in v2.

Patch 3/3 runs the already existing udp zerocopy tests
  as part of kselftest

See also recent Linux Plumbers presentation
  https://linuxplumbersconf.org/event/2/contributions/106/attachments/104/128/willemdebruijn-lpc2018-udpgso-presentation-20181113.pdf

Changes:
  v1 -> v2
    - Fixup reverse christmas tree violation
  v2 -> v3
    - Split refcount avoidance optimization into separate patch
      - Fix refcount leak on error in fragmented case
        (thanks to Paolo Abeni for pointing this one out!)
      - Fix refcount inc on zero
  v3 -> v4
    - Move skb_zcopy_set below the only kfree_skb that might cause
      a premature uarg destroy before skb_zerocopy_put_abort
      - Move the entire skb_shinfo assignment block, to keep that
	cacheline access in one place

Willem de Bruijn (3):
  udp: msg_zerocopy
  udp: elide zerocopy operation in hot path
  selftests: extend zerocopy tests to udp

 include/linux/skbuff.h                      | 13 +++++---
 net/core/skbuff.c                           | 15 ++++++---
 net/core/sock.c                             |  5 ++-
 net/ipv4/ip_output.c                        | 37 ++++++++++++++++-----
 net/ipv4/tcp.c                              |  2 +-
 net/ipv6/ip6_output.c                       | 37 ++++++++++++++++-----
 tools/testing/selftests/net/msg_zerocopy.c  |  3 +-
 tools/testing/selftests/net/msg_zerocopy.sh |  2 ++
 tools/testing/selftests/net/udpgso_bench.sh |  3 ++
 9 files changed, 90 insertions(+), 27 deletions(-)

-- 
2.20.0.rc1.387.gf8505762e3-goog