From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH] user_ns: Improve the user_ns on-the-slab packaging
Date: Tue, 7 Dec 2010 14:13:15 -0800
Message-ID: <20101207141315.5ea45abf.akpm@linux-foundation.org>
References: <4CFE40D1.5000309@parallels.com>
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To: Pavel Emelyanov <xemul@parallels.com>
Cc: Linux Containers <containers@lists.osdl.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, "Serge E. Hallyn" <serge@hallyn.com>
List-Id: containers.vger.kernel.org

On Tue, 07 Dec 2010 17:12:33 +0300
Pavel Emelyanov <xemul@parallels.com> wrote:

> @@ -126,3 +128,11 @@ gid_t user_ns_map_gid(struct user_namespace *to, const struct cred *cred, gid_t
>  	/* No useful relationship so no mapping */
>  	return overflowgid;
>  }
> +
> +static __init int user_namespaces_init(void)
> +{
> +	user_ns_cachep = KMEM_CACHE(user_namespace, SLAB_PANIC);
> +	return 0;
> +}
> +
> +__initcall(user_namespaces_init);

checkpatch (which you apparently didn't use) says

WARNING: please use device_initcall() instead of __initcall()
#81: FILE: kernel/user_namespace.c:138:
+__initcall(user_namespaces_init);

which was a somewhat random recommendation.  I think I'll switch it to
plain old module_init().

Presumably user-namespaces don't get used prior to initcalls being run.