backports: backport frag helper functions for mem limit tracking

backports: backport frag helper functions for mem limit tracking

Jesper added frag helper functions through commit d433673e5f
added on. This is a straight forward backport using the LINUX_BACKPORT()
namespace.

mcgrof@ergon ~/linux-next (git::master)$ git describe --contains d433673e5f
v3.9-rc1~139^2~232^2~2

commit d433673e5f9180e05a770c4b2ab18c08ad51cc21
Author: Jesper Dangaard Brouer <brouer@redhat.com>
Date:   Mon Jan 28 23:45:12 2013 +0000

    net: frag helper functions for mem limit tracking

    This change is primarily a preparation to ease the extension of memory
    limit tracking.

    The change does reduce the number atomic operation, during freeing of
    a frag queue.  This does introduce a some performance improvement, as
    these atomic operations are at the core of the performance problems
    seen on NUMA systems.

    Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Luis R. Rodriguez <mcgrof@do-not-panic.com>