From e756c7b698604f11a979f2781d06eb7b80aba363 Mon Sep 17 00:00:00 2001
From: Zefan Li <lizefan@huawei.com>
Date: Fri, 26 Sep 2014 12:03:25 +0800
Subject: [PATCH] Revert "cgroup: remove redundant variable in cgroup_mount()"

This reverts commit 0c7bf3e8cab7900e17ce7f97104c39927d835469.

If there are child cgroups in the cgroupfs and then we umount it,
the superblock will be destroyed but the cgroup_root will be kept
around. When we mount it again, cgroup_mount() will find this
cgroup_root and allocate a new sb for it.

So with this commit we will be trapped in a dead loop in the case
described above, because kernfs_pin_sb() keeps returning NULL.

Currently I don't see how we can avoid using both pinned_sb and
new_sb, so just revert it.

Cc: Al Viro <viro@ZenIV.linux.org.uk>
Reported-by: Andrey Wagin <avagin@gmail.com>
Signed-off-by: Zefan Li <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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