Re: [PATCH] Revert "cgroup: remove redundant variable in cgroup_mount()"

From: Tejun Heo
Date: Fri Sep 26 2014 - 00:26:27 EST

On Fri, Sep 26, 2014 at 12:03:25PM +0800, Zefan Li wrote:
> 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@xxxxxxxxxxxxxxxxxx>
> Reported-by: Andrey Wagin <avagin@xxxxxxxxx>
> Signed-off-by: Zefan Li <lizefan@xxxxxxxxxx>

Applied to cgroup/for-3.18.


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