Re: [RFC][PATCH 2/4] sunrpc: Use utsnamespaces

[Serge E. Hallyn]

Quoting Matt Helsley (matthltc@xxxxxxxxxx):
> We can often specify the UTS namespace to use when starting an RPC client.
> However sometimes no UTS namespace is available (specifically during system
> shutdown as the last NFS mount in a container is unmounted) so fall
> back to the initial UTS namespace.

So what happens if we take this patch and do nothing else?

The only potential problem situation will be rpc requests
made on behalf of a container in which the last task has
exited, right?  So let's say a container did an nfs mount
and then exits, causing an nfs umount request.

That umount request will now be sent with the wrong nodename.
Does that actually cause problems, will the server use the
nodename to try and determine the client sending the request?

thanks,
-serge

> Signed-off-by: Matt Helsley <matthltc@xxxxxxxxxx>
> Cc: Cedric Le Goater <clg@xxxxxxxxxx>
> Cc: Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>
> Cc: linux-nfs@xxxxxxxxxxxxxxx
> Cc: Trond Myklebust <trond.myklebust@xxxxxxxxxx>
> Cc: Chuck Lever <chuck.lever@xxxxxxxxxx>
> Cc: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
> Cc: Linux Containers <containers@xxxxxxxxxxxxxx>
> 
> ---
>  net/sunrpc/clnt.c |    7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> Index: linux-2.6.28/net/sunrpc/clnt.c
> ===================================================================
> --- linux-2.6.28.orig/net/sunrpc/clnt.c
> +++ linux-2.6.28/net/sunrpc/clnt.c
> @@ -128,6 +128,7 @@ static struct rpc_clnt * rpc_new_client(
>  	struct rpc_version	*version;
>  	struct rpc_clnt		*clnt = NULL;
>  	struct rpc_auth		*auth;
> +	struct new_utsname	*uts_ns = init_utsname();
>  	int err;
>  	size_t len;
> 
> @@ -213,10 +214,12 @@ static struct rpc_clnt * rpc_new_client(
>  	}
> 
>  	/* save the nodename */
> -	clnt->cl_nodelen = strlen(init_utsname()->nodename);
> +	if (current->nsproxy != NULL)
> +		uts_ns = utsname();
> +	clnt->cl_nodelen = strlen(uts_ns->nodename);
>  	if (clnt->cl_nodelen > UNX_MAXNODENAME)
>  		clnt->cl_nodelen = UNX_MAXNODENAME;
> -	memcpy(clnt->cl_nodename, init_utsname()->nodename, clnt->cl_nodelen);
> +	memcpy(clnt->cl_nodename, uts_ns->nodename, clnt->cl_nodelen);
>  	rpc_register_client(clnt);
>  	return clnt;
> 
> 
> -- 
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