linux-kernel - Re: [PATCH] cgroups: fix API thinko

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Message-ID: <4C6A3812.1070002@cn.fujitsu.com>
Date:	Tue, 17 Aug 2010 15:19:46 +0800
From:	Li Zefan <lizf@...fujitsu.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>
CC:	Paul Menage <menage@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ben Blum <bblum@...gle.com>,
	containers@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org,
	Alex Williamson <alex.williamson@...hat.com>,
	kvm@...r.kernel.org
Subject: Re: [PATCH] cgroups: fix API thinko

(Just came back from vacation)

Michael S. Tsirkin wrote:
> cgroup_attach_task_current_cg API that have upstream is backwards: we
> really need an API to attach to the cgroups from another process A to
> the current one.
> 
> In our case (vhost), a priveledged user wants to attach it's task to cgroups
> from a less priveledged one, the API makes us run it in the other
> task's context, and this fails.
> 
> So let's make the API generic and just pass in 'from' and 'to' tasks.
> Add an inline wrapper for cgroup_attach_task_current_cg to avoid
> breaking bisect.
> 
> Signed-off-by: Michael S. Tsirkin <mst@...hat.com>

Acked-by: Li Zefan <lizf@...fujitsu.com>

I also don't like the name, but I'm not good at English or naming. ;)

> ---
> 
> Paul, Li, Sridhar, could you please review the following
> patch?
> 
> I only compile-tested it due to travel, but looks
> straight-forward to me.
> Alex Williamson volunteered to test and report the results.
> Sending out now for review as I might be offline for a bit.
> Will only try to merge when done, obviously.
> 
> If OK, I would like to merge this through -net tree,
> together with the patch fixing vhost-net.
> Let me know if that sounds ok.
> 

That's Ok.

...
> diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
> index 43b2072..b38ec60 100644
> --- a/include/linux/cgroup.h
> +++ b/include/linux/cgroup.h
> @@ -525,7 +525,11 @@ struct task_struct *cgroup_iter_next(struct cgroup *cgrp,
>  void cgroup_iter_end(struct cgroup *cgrp, struct cgroup_iter *it);
>  int cgroup_scan_tasks(struct cgroup_scanner *scan);
>  int cgroup_attach_task(struct cgroup *, struct task_struct *);
> -int cgroup_attach_task_current_cg(struct task_struct *);
> +int cgroup_attach_task_all(struct task_struct *from, struct task_struct *);

a nitpick:

better add a blank line here.

> +static inline int cgroup_attach_task_current_cg(struct task_struct *tsk)
> +{
> +	return cgroup_attach_task_all(current, tsk);
> +}
--
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