Tejun Heo wrote:

Hey, Li.

On Fri, Mar 30, 2012 at 08:42:07PM +0800, Li Zefan wrote:

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This patch replaces cgroup file interface with cftype based one which
allows dynamic additions and removals of cftype arrays whether the
target subsystem is attached or not.  This can be used to make subsys
rebinding via remount work properly but I intentionally avoided doing
that at the moment.

What's the problem with remount?

Subsys can't be changed if any non-root cgroup exists.

Ah, this is a long-standing defect, which is documented in Doc/../cgroups.txt.
It's not trivial to fix it, and I never heard someone request it to be fixed.

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and is it important enough that it should be fixed even the feature
is marked as deprecated?

I'm not sure.  We *might* need it during multi-mount -> single-mount
transition depending on how that's implemented, so the "at the moment"
qualifier.  It probably won't be fixed but I'm not fully sure.

fine.

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This makes cgroup population simpler for controllers and will be used
to allow controllers to be more dynamic.  e.g. blkio subsys has
sub-policies which may come and go while blkio subsys is attached and
it currently uses fixed set of files which stays blank if not in use.

Dynamic cgroup files was mentioned before. The scenario in mind was blkio
control files can be added/removed automatically as devices come and ago.

So this time blkio subsystem is really going to be made more dynamic
soon?

Patchset already posted.

  http://thread.gmane.org/gmane.linux.kernel.cgroups/1376

Thanks!