Introduce possible_net_t

The current usage of write_pnet and read_pnet is a little laborious and error prone as you only notice if you failed to include them if are compiling with network namespaces enabled.

possible_net_t remedies that by using a type that is 0 bytes when network namespaces are disabled and can only be read and written to with read_pnet and write_pnet.

Aka less work and safer for the same effect.

I kill hold_net and release_net first as are they are haven't been used since 2008 and are noise at the points where write_pnet and read_pnet are used.

I have folded in Eric Dumazets suggestions to improve the killing of hold_net and release net. And respon. I had to respin anyway as there was enough changes elsewhere in the tree the previous version of these patches did not quite apply cleanly.

Eric W. Biederman (2):
net: Kill hold_net release_net
net: Introduce possible_net_t

 include/linux/netdevice.h            |  9 ++-----
 include/net/cfg80211.h               |  4 +--
 include/net/fib_rules.h              |  9 +------
 include/net/genetlink.h              |  4 +--
 include/net/inet_hashtables.h        |  4 +--
 include/net/ip_vs.h                  |  8 +++---
 include/net/neighbour.h              |  8 ++----
 include/net/net_namespace.h          | 52 +++++++++---------------------------
 include/net/netfilter/nf_conntrack.h |  5 ++--
 include/net/sock.h                   |  6 ++---
 include/net/xfrm.h                   |  8 ++----
 net/9p/trans_fd.c                    |  4 +--
 net/core/dev.c                       |  2 --
 net/core/fib_rules.c                 | 17 +++---------
 net/core/neighbour.c                 |  9 ++-----
 net/core/net_namespace.c             | 11 --------
 net/core/sock.c                      |  1 -
 net/ipv4/fib_semantics.c             |  3 +--
 net/ipv4/inet_hashtables.c           |  3 +--
 net/ipv4/inet_timewait_sock.c        |  3 +--
 net/ipv4/ipmr.c                      |  4 +--
 net/ipv6/addrlabel.c                 | 11 ++------
 net/ipv6/ip6_flowlabel.c             |  3 +--
 net/ipv6/ip6mr.c                     |  4 +--
 net/openvswitch/datapath.c           |  4 +--
 net/openvswitch/datapath.h           |  4 +--
 net/packet/internal.h                |  4 +--
 27 files changed, 49 insertions(+), 155 deletions(-)