[Devel] Re: [PATCH] cgroup: notify ns_cgroup deprecated

[Paul Menage]

On Wed, Sep 29, 2010 at 2:21 PM, Daniel Lezcano <daniel.lezcano at free.fr> wrote:
> 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 at free.fr>

Acked-by: Paul Menage <menage at google.com>

> ---
>  Documentation/feature-removal-schedule.txt |   17 +++++++++++++++++
>  kernel/ns_cgroup.c                         |    8 ++++++++
>  2 files changed, 25 insertions(+), 0 deletions(-)
>
> diff --git a/Documentation/feature-removal-schedule.txt b/Documentation/feature-removal-schedule.txt
> index b32911b..a39e2f3 100644
> --- a/Documentation/feature-removal-schedule.txt
> +++ b/Documentation/feature-removal-schedule.txt
> @@ -545,4 +545,21 @@ Why:    This is a legacy interface which have been replaced by a more
>  Who:    NeilBrown <neilb at suse.de>
>
>  ----------------------------
> +
> +What:   namespace cgroup (ns_cgroup)
> +When:   2.6.38
> +Why:    The ns_cgroup leads to some problems:
> +       * cgroup creation is out-of-control
> +       * cgroup name can conflict when pids are looping
> +       * it is not possible to have a single process handling
> +       a lot of namespaces without falling in a exponential creation time
> +       * we may want to create a namespace without creating a cgroup
> +
> +       The ns_cgroup is replaced by a compatibility flag 'clone_children',
> +       where a newly created cgroup will copy the parent cgroup values.
> +       The userspace has to manually create a cgroup and add a task to
> +       the 'tasks' file.
> +Who:    Daniel Lezcano <daniel.lezcano at free.fr>
> +
> +----------------------------
>
> diff --git a/kernel/ns_cgroup.c b/kernel/ns_cgroup.c
> index 2a5dfec..2c98ad9 100644
> --- a/kernel/ns_cgroup.c
> +++ b/kernel/ns_cgroup.c
> @@ -85,6 +85,14 @@ static struct cgroup_subsys_state *ns_create(struct cgroup_subsys *ss,
>                return ERR_PTR(-EPERM);
>        if (!cgroup_is_descendant(cgroup, current))
>                return ERR_PTR(-EPERM);
> +       if (test_bit(CGRP_CLONE_CHILDREN, &cgroup->flags)) {
> +               printk("ns_cgroup can't be created with parent "
> +                      "'clone_children' set.\n");
> +               return ERR_PTR(-EINVAL);
> +       }
> +
> +       printk_once("ns_cgroup deprecated: consider using the "
> +                   "'clone_children' flag without the ns_cgroup.\n");
>
>        ns_cgroup = kzalloc(sizeof(*ns_cgroup), GFP_KERNEL);
>        if (!ns_cgroup)
> --
> 1.7.0.4
>
>
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