On Wed 31-10-12 10:04:31, Tejun Heo wrote:
> Hey, Michal.
>
> On Wed, Oct 31, 2012 at 04:55:14PM +0100, Michal Hocko wrote:
> > > + /*
> > > + * Only live parents can have children. Note that the liveliness
> > > + * check isn't strictly necessary because cgroup_mkdir() and
> > > + * cgroup_rmdir() are fully synchronized by i_mutex; however, do it
> > > + * anyway so that locking is contained inside cgroup proper and we
> > > + * don't get nasty surprises if we ever grow another caller.
> > > + */
> > > + if (!cgroup_lock_live_group(parent)) {
> > > + err = -ENODEV;
> > > + goto err_free;
> > > + }
> > > +
> >
> > I think this should be moved up before we try to allocate any memory.
> > Or is your motivation to keep cgroup_lock held for shorter time?
> > I could agree with that but a small comment would be helpful.
>
> Then I have to change the error out path more and I'm not sure I wanna
> call deactivate_super() under cgroup_mutex. It's just simpler this
> way.
I am not sure I understand. What does deactivate_super has to do with
the above suggestion? cgroup_lock_live_group will take the cgroup_mutex
on the success or frees the previously allocated&unused memory. The
only thing I was suggesting is to do cgroup_lock_live_group first and
allocate the cgroup only if it doesn't fail.
--
Michal Hocko
SUSE Labs
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