Re: [PATCH 11/11] lockd: Allow mount option to specify caller_name

[Trond Myklebust <trond.myklebust@fys.uio.no>]

On Thu, 2010-04-01 at 15:04 -0400, Chuck Lever wrote: 
> NLMPROC_LOCK requests have a "caller_name" argument which is supposed
> to contain the hostname the server uses to call the client back.
> Linux simply stuffs the system's utsname in this field, but this is
> not always the correct choice.  For example:
> 
>   o  If an unqualified hostname is used for the client's utsname,
>      it could be ambiguous when the server tries to resolve it
>   o  If the client's actual hostname is determined by DHCP, it may
>      not match its utsname
>   o  If the NFS mount was done in a network namespace, the namespace
>      name won't match the client's utsname
>   o  If the client has multiple network interfaces, it should provide
>      a hostname that matches the source address used to contact the
>      server
> 
> In all of these cases, user space can determine the correct value of
> the caller_name argument at mount time.
> 
> So, add a mount option that allows user space to specify the value of
> the caller_name argument of NLMPROC_LOCK requests.  If not specified,
> the kernel continues to use the init utsname, as before.

This argument makes no sense. Mount points do _not_ follow network
namespace boundaries, so making this hostname of yours a mount option
will make matters worse, not better.

Furthermore, even if we were to accept your argument, you are not
matching nfs_clients to your "namespace name", so if you do have more
than 1 mount to the same server but from different namespaces, then the
namespace name of the first to mount will automatically become the
default for the second mount too.

Trond