Subject: Re: [PATCH v2 00/12] make rpc_pipefs be mountable multiple time

From: Rob Landley <[email-masked]>
Date: Thu, 30 Dec 2010 04:05:07 -0600

On 12/30/2010 03:44 AM, Kirill A. Shutemov wrote:
>>> If no rpcmount mountoption, no rpc_pipefs was found at
>>> '/var/lib/nfs/rpc_pipefs' and we are in init's mount namespace, we use
>>> init_rpc_pipefs.
>>
>> It's the "we are in init's mount namespace" that I was wondering about.
>>
>> So if I naievely chroot, nfs mount stops working the way it did before I
>> chrooted unless I do an extra setup step?
>
> No. It will work as before since you are still in init's mount namespace.
> Creating new mount namespace changes rules.

Ah, CLONE_NEWNS and then you need /var/lib/nfs/rpc_pipefs.  Got it.

I'm kind of surprised that the kernel cares about a specific path under 
/var/lib.  (Seems like policy in the kernel somehow.)  Can't it just 
check the current process's mount list to see if an instance of 
rpc_pipefs is mounted in the current namespace the way lxc looks for 
cgroups?  Or are there potential performance/scalability issues with that?

Rob