Merge branch 'sctp-fully-support-memory-accounting'

Xin Long says:

====================
sctp: fully support memory accounting

sctp memory accounting is added in this patchset by using
these kernel APIs on send side:

  - sk_mem_charge()
  - sk_mem_uncharge()
  - sk_wmem_schedule()
  - sk_under_memory_pressure()
  - sk_mem_reclaim()

and these on receive side:

  - sk_mem_charge()
  - sk_mem_uncharge()
  - sk_rmem_schedule()
  - sk_under_memory_pressure()
  - sk_mem_reclaim()

With sctp memory accounting, we can limit the memory allocation by
either sysctl:

  # sysctl -w net.sctp.sctp_mem="10 20 50"

or cgroup:

  # echo $((8<<14)) > \
    /sys/fs/cgroup/memory/sctp_mem/memory.kmem.tcp.limit_in_bytes

When the socket is under memory pressure, the send side will block
and wait, while the receive side will renege or drop.

v1->v2:
  - add the missing Reported/Tested/Acked/-bys.
====================

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