Merge branch 'for-2.6.38/rc2-holder' into for-2.6.38/core

 Limits for writes can be put using blkio.write_bps_device file.

Hierarchical Cgroups

====================

- Currently none of the IO control policy supports hierarhical groups. But

  cgroup interface does allow creation of hierarhical cgroups and internally

  IO policies treat them as flat hierarchy.

  So this patch will allow creation of cgroup hierarhcy but at the backend

  everything will be treated as flat. So if somebody created a hierarchy like

  as follows.

			root

			/  \

		     test1 test2

			|

		     test3

  CFQ and throttling will practically treat all groups at same level.

				pivot

			     /  |   \  \

			root  test1 test2  test3

  Down the line we can implement hierarchical accounting/control support

  and also introduce a new cgroup file "use_hierarchy" which will control

  whether cgroup hierarchy is viewed as flat or hierarchical by the policy..

  This is how memory controller also has implemented the things.

Various user visible config options

===================================

CONFIG_BLK_CGROUP

		goto done;

	}

	/* Currently we do not support hierarchy deeper than two level (0,1) */

	if (parent != cgroup->top_cgroup)

		return ERR_PTR(-EPERM);

	blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL);

	if (!blkcg)

		return ERR_PTR(-ENOMEM);