Re: [PATCH 3/20] Introduce MS_KERNMOUNT flag

[Pavel Emelyanov <xemul-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org>]

Christoph Hellwig wrote:
> On Fri, Aug 10, 2007 at 03:47:55PM +0400, xemul-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org wrote:
>> This flag tells the .get_sb callback that this is a kern_mount() call
>> so that it can trust *data pointer to be valid in-kernel one. If this
>> flag is passed from the user process, it is cleared since the *data
>> pointer is not a valid kernel object.
>>
>> Running a few steps forward - this will be needed for proc to create the
>> superblock and store a valid pid namespace on it during the namespace
>> creation. The reason, why the namespace cannot live without proc mount
>> is described in the appropriate patch.
> 
> I don't like this at all.  We should never pass kernel and userspace
> addresses through the same pointer.  Maybe add an additional argument
> to the get_sb prototype instead.  But this whole idea of mounting /proc
> from kernelspace sounds like a really bad idea to me.  /proc should
> never be mounted from the kernel but always normally from userspace.

Why then is it mounted in proc_root_init()?

Thanks,
Pavel