Re: [PATCH RESEND] userns: enable tmpfs support for user namespace

[Serge Hallyn <serge.hallyn-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org>]

Quoting Gao feng (gaofeng-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org):
> From: gaofeng <gaofeng-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org>
> 
> Since the memory used by tmpfs is under control of
> memory cgroup. and the files under the tmpfs will not
> be leak to other tmpfs.
> 
> So mounting tmpfs in user namespace does no harm to the
> host,we can allow tmpfs to be mounted in user namespace.
> 
> Signed-off-by: gaofeng <gaofeng-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org>

I've got the same patch in my kernel at
http://kernel.ubuntu.com/git?p=serge/quantal-userns.git;a=summary

except note that there are two definitions of shmem_fs_type.

> ---
>  mm/shmem.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/mm/shmem.c b/mm/shmem.c
> index 5dd56f6..8eff60a 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -2766,6 +2766,7 @@ static struct file_system_type shmem_fs_type = {
>  	.name		= "tmpfs",
>  	.mount		= shmem_mount,
>  	.kill_sb	= kill_litter_super,
> +	.fs_flags	= FS_USERNS_MOUNT,
>  };
>  
>  int __init shmem_init(void)
> -- 
> 1.7.11.7
>