Merge branch 'RDS-zerocopy-code-enhancements'

Merge branch 'RDS-zerocopy-code-enhancements'

Sowmini Varadhan says:

====================
RDS: zerocopy code enhancements

A couple of enhancements to the rds zerocop code
- patch 1 refactors rds_message_copy_from_user to pull the zcopy logic
  into its own function
- patch 2 drops the usage sk_buff to track MSG_ZEROCOPY cookies and
  uses a simple linked list (enhancement suggested by willemb during
  code review)
====================

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