From 755bf5ee8633b97d8fd0ffbb4221662056dda22b Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Tue, 18 Nov 2014 02:49:50 -0500
Subject: [PATCH] cgroup: restructure child_subsys_mask handling in
 cgroup_subtree_control_write()

Make cgroup_subtree_control_write() first calculate new
subtree_control (new_sc), child_subsys_mask (new_ss) and
css_enable/disable masks before applying them to the cgroup.  Also,
store the original subtree_control (old_sc) and child_subsys_mask
(old_ss) and use them to restore the orignal state after failure.

This patch shouldn't cause any behavior changes.  This prepares for a
fix for a bug in the async css offline wait logic.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Zefan Li <lizefan@huawei.com>
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