Re: [PATCH -mmotm 1/8] cgroup: introduce cancel_attach()

[Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>]

On Mon, 09 Nov 2009 15:23:02 +0800, Li Zefan <lizf@cn.fujitsu.com> wrote:
> Daisuke Nishimura wrote:
> > This patch adds cancel_attach() operation to struct cgroup_subsys.
> > cancel_attach() can be used when can_attach() operation prepares something
> > for the subsys, but we should rollback what can_attach() operation has prepared
> > if attach task fails after we've succeeded in can_attach().
> > 
> > Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
> 
> Acked-by: Li Zefan <lizf@cn.fujitsu.com>
> 
Thank you for your ack.

> > ---
> >  Documentation/cgroups/cgroups.txt |   13 +++++++++++-
> >  include/linux/cgroup.h            |    2 +
> >  kernel/cgroup.c                   |   38 ++++++++++++++++++++++++++++++------
> >  3 files changed, 45 insertions(+), 8 deletions(-)
> > 
> > diff --git a/Documentation/cgroups/cgroups.txt b/Documentation/cgroups/cgroups.txt
> > index 0b33bfe..c86947c 100644
> > --- a/Documentation/cgroups/cgroups.txt
> > +++ b/Documentation/cgroups/cgroups.txt
> > @@ -536,10 +536,21 @@ returns an error, this will abort the attach operation.  If a NULL
> >  task is passed, then a successful result indicates that *any*
> >  unspecified task can be moved into the cgroup. Note that this isn't
> >  called on a fork. If this method returns 0 (success) then this should
> > -remain valid while the caller holds cgroup_mutex. If threadgroup is
> > +remain valid while the caller holds cgroup_mutex and it is ensured that either
> > +attach() or cancel_attach() will be called in futer. If threadgroup is
> 
> s/futer/future
> 
Ah, I'm sorry.
will fix.

> >  true, then a successful result indicates that all threads in the given
> >  thread's threadgroup can be moved together.
> ...
> > +out:
> > +	if (retval)
> 
> I prefer:
> 
> 	if (reval) {
> 		...
> 	}
> 
Okey.
will change in next post.


Thanks,
Daisuke Nishimura.

> > +		for_each_subsys(root, ss) {
> > +			if (ss == failed_ss)
> > +				/*
> > +				 * This means can_attach() of this subsystem
> > +				 * have failed, so we don't need to call
> > +				 * cancel_attach() against rests of subsystems.
> > +				 */
> > +				break;
> > +			if (ss->cancel_attach)
> > +				ss->cancel_attach(ss, cgrp, tsk, false);
> > +		}
> > +	return retval;
> >  }
> >  
> >  /*

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