linux-kernel - Re: [PATCH] xenbus: Use proc_create_mount

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Date:   Tue, 30 Aug 2016 16:48:08 +0200
From:   Juergen Gross <jgross@...e.com>
To:     Seth Forshee <seth.forshee@...onical.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        David Vrabel <david.vrabel@...rix.com>
Cc:     xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] xenbus: Use proc_create_mount_point() to create /proc/xen

On 29/08/16 17:03, Seth Forshee wrote:
> Mounting proc in user namespace containers fails if the xenbus
> filesystem is mounted on /proc/xen because this directory fails
> the "permanently empty" test. proc_create_mount_point() exists
> specifically to create such mountpoints in proc but is currently
> proc-internal. Export this interface to modules, then use it in
> xenbus when creating /proc/xen.
> 
> Signed-off-by: Seth Forshee <seth.forshee@...onical.com>
> ---
>  drivers/xen/xenbus/xenbus_probe.c | 2 +-
>  fs/proc/generic.c                 | 1 +
>  fs/proc/internal.h                | 1 -
>  include/linux/proc_fs.h           | 2 ++
>  4 files changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c
> index 33a31cfef55d..b5c1dec4a7c2 100644
> --- a/drivers/xen/xenbus/xenbus_probe.c
> +++ b/drivers/xen/xenbus/xenbus_probe.c
> @@ -826,7 +826,7 @@ static int __init xenbus_init(void)
>  	 * Create xenfs mountpoint in /proc for compatibility with
>  	 * utilities that expect to find "xenbus" under "/proc/xen".
>  	 */
> -	proc_mkdir("xen", NULL);
> +	proc_create_mount_point("xen");
>  #endif
>  
>  out_error:
> diff --git a/fs/proc/generic.c b/fs/proc/generic.c
> index c633476616e0..be014c544d50 100644
> --- a/fs/proc/generic.c
> +++ b/fs/proc/generic.c
> @@ -477,6 +477,7 @@ struct proc_dir_entry *proc_create_mount_point(const char *name)
>  	}
>  	return ent;
>  }
> +EXPORT_SYMBOL(proc_create_mount_point);

EXPORT_SYMBOL_GPL()?

Juergen