Re: [PATCH] cgroup : remove the ns_cgroup

From: Daniel Lezcano
Date: Thu Jan 27 2011 - 03:51:02 EST

On 01/27/2011 02:45 AM, Andrew Morton wrote:
On Thu, 27 Jan 2011 09:08:51 +0800 Li Zefan<lizf@xxxxxxxxxxxxxx> wrote:

Andrew Morton wrote:
On Tue, 25 Jan 2011 10:39:48 +0100
Daniel Lezcano<daniel.lezcano@xxxxxxx> wrote:

This patch removes the ns_cgroup as suggested in the following thread:
I had this patch queued up in September last year, but dropped it. Why
did I do that?
Because you wanted to wait for some time for users (if any) to notice this
coming change.

Author: Daniel Lezcano<daniel.lezcano@xxxxxxx>
Date: Wed Oct 27 15:33:38 2010 -0700

cgroup: notify ns_cgroup deprecated

The ns_cgroup will be removed very soon. Let's warn, for this version,
ns_cgroup is deprecated.

Make ns_cgroup and clone_children exclusive. If the clone_children is set
and the ns_cgroup is mounted, let's fail with EINVAL when the ns_cgroup
subsys is created (a printk will help the user to understand why the
creation fails).

Update the feature remove schedule file with the deprecated ns_cgroup.

Signed-off-by: Daniel Lezcano<daniel.lezcano@xxxxxxx>
Acked-by: Paul Menage<menage@xxxxxxxxxx>
Signed-off-by: Andrew Morton<akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds<torvalds@xxxxxxxxxxxxxxxxxxxx>
ooh, that was clever of me.

Here is the text which was missing from the changelog:

This is a userspace-visible change. Commit 45531757b45c ("cgroup:
notify ns_cgroup deprecated") (merged into 2.6.27) caused the kernel
to emit a printk warning users that the feature is planned for
removal. Since that time we have heard from XXX users who were
affected by this.

Please provide XXX.

Ok, AFAIK nobody makes use of the ns_cgroup except the LXC userspace tools which I maintain and where
the backward compatibility with the ns_cgroup and the clone_children flag is already implemented.
Since today nobody seems to be affected by this.

I Cc'ed the libvirt mailing list.

How do we know that 2.6.37->2.6.38 is long enough? Will any major
distros be released containing this warning in that timeframe? I doubt

Hmm, maybe it is too short but I don't think someone will complain about this feature removal.
Google chromium is using the namespaces, hence a lot of cgroup is created on the system. The vsftpd and some pam modules uses the namespaces too.
I won't be surprised if one of these applications fails with 'clone' returning EEXIST ...

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