memcg: add HugeTLB extension

memcg: add HugeTLB extension

This patch implements a memcg extension that allows us to control HugeTLB
allocations via memory controller.  The extension allows to limit the
HugeTLB usage per control group and enforces the controller limit during
page fault.  Since HugeTLB doesn't support page reclaim, enforcing the
limit at page fault time implies that, the application will get SIGBUS
signal if it tries to access HugeTLB pages beyond its limit.  This
requires the application to know beforehand how much HugeTLB pages it
would require for its use.

The charge/uncharge calls will be added to HugeTLB code in later patch.
Support for memcg removal will be added in later patches.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Hillf Danton <dhillf@gmail.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>