linux-kernel - Re: [PATCH 7/8] cgroup: mount cgroupns-root when inside non-init cgroupns

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Message-ID: <20151202165637.GA20840@mail.hallyn.com>
Date:	Wed, 2 Dec 2015 10:56:37 -0600
From:	"Serge E. Hallyn" <serge.hallyn@...ntu.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	"Serge E. Hallyn" <serge.hallyn@...ntu.com>, serge@...lyn.com,
	linux-kernel@...r.kernel.org, adityakali@...gle.com,
	linux-api@...r.kernel.org, containers@...ts.linux-foundation.org,
	cgroups@...r.kernel.org, lxc-devel@...ts.linuxcontainers.org,
	akpm@...ux-foundation.org, ebiederm@...ssion.com
Subject: Re: [PATCH 7/8] cgroup: mount cgroupns-root when inside non-init
 cgroupns

On Wed, Dec 02, 2015 at 11:53:12AM -0500, Tejun Heo wrote:
> Hello, Serge.
> 
> On Tue, Dec 01, 2015 at 03:58:53PM -0600, Serge E. Hallyn wrote:
> > I mispoke before though - it's not the hierarchy's root dentry,
> > but rather a dentry for a descendent cgroup which will become the
> > root dentry for the new superblock.  We do know that there must be
> > a css_set with a cgroup.  I'm still trying to track down whether
> > that cgrou's inode's dentry can ever be flushed.  I would think
> > not but am not sure.
> 
> Hmmm... I'm not really following.  The inode can be flushed and that's
> why it needs to be walked down from root.  What am I missing here?

Can it be flushed when we know that the cgroup is being pinned by
a css_set?  (There's either a task or a cgroup_namespace pinning it
or we wouldn't get here)

-serge
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