netdev - Re: [PATCH v2 3/5] SUNRPC: make RPC service dependable on rpcbind clients creation

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Date:	Fri, 9 Sep 2011 10:07:45 -0400
From:	Jeff Layton <jlayton@...hat.com>
To:	Stanislav Kinsbursky <skinsbursky@...allels.com>
Cc:	Trond.Myklebust@...app.com, linux-nfs@...r.kernel.org,
	xemul@...allels.com, neilb@...e.de, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, bfields@...ldses.org,
	davem@...emloft.net
Subject: Re: [PATCH v2 3/5] SUNRPC: make RPC service dependable on rpcbind
 clients creation

On Fri, 09 Sep 2011 16:08:44 +0400
Stanislav Kinsbursky <skinsbursky@...allels.com> wrote:

> Create rcbind clients or increase rpcbind users counter during RPC service
> creation and decrease this counter (and possibly destroy those clients) on RPC
> service destruction.
> 
> Signed-off-by: Stanislav Kinsbursky <skinsbursky@...allels.com>
> 
> ---
>  include/linux/sunrpc/clnt.h |    2 ++
>  net/sunrpc/rpcb_clnt.c      |    2 +-
>  net/sunrpc/svc.c            |   13 +++++++++++--
>  3 files changed, 14 insertions(+), 3 deletions(-)
> 
> diff --git a/include/linux/sunrpc/clnt.h b/include/linux/sunrpc/clnt.h
> index db7bcaf..65a8115 100644
> --- a/include/linux/sunrpc/clnt.h
> +++ b/include/linux/sunrpc/clnt.h
> @@ -135,10 +135,12 @@ void		rpc_shutdown_client(struct rpc_clnt *);
>  void		rpc_release_client(struct rpc_clnt *);
>  void		rpc_task_release_client(struct rpc_task *);
>  
> +int		rpcb_create_local(void);
>  int		rpcb_register(u32, u32, int, unsigned short);
>  int		rpcb_v4_register(const u32 program, const u32 version,
>  				 const struct sockaddr *address,
>  				 const char *netid);
> +void		rpcb_put_local(void);
>  void		rpcb_getport_async(struct rpc_task *);
>  
>  void		rpc_call_start(struct rpc_task *);
> diff --git a/net/sunrpc/rpcb_clnt.c b/net/sunrpc/rpcb_clnt.c
> index b4cc0f1..437ec60 100644
> --- a/net/sunrpc/rpcb_clnt.c
> +++ b/net/sunrpc/rpcb_clnt.c
> @@ -318,7 +318,7 @@ out:
>   * Returns zero on success, otherwise a negative errno value
>   * is returned.
>   */
> -static int rpcb_create_local(void)
> +int rpcb_create_local(void)
>  {
>  	static DEFINE_MUTEX(rpcb_create_local_mutex);
>  	int result = 0;
> diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
> index 6a69a11..9095c0e 100644
> --- a/net/sunrpc/svc.c
> +++ b/net/sunrpc/svc.c
> @@ -367,8 +367,11 @@ __svc_create(struct svc_program *prog, unsigned int bufsize, int npools,
>  	unsigned int xdrsize;
>  	unsigned int i;
>  
> -	if (!(serv = kzalloc(sizeof(*serv), GFP_KERNEL)))
> +	if (rpcb_create_local() < 0)
>  		return NULL;
> +
> +	if (!(serv = kzalloc(sizeof(*serv), GFP_KERNEL)))
> +		goto out_err;
>  	serv->sv_name      = prog->pg_name;
>  	serv->sv_program   = prog;
>  	serv->sv_nrthreads = 1;
> @@ -403,7 +406,7 @@ __svc_create(struct svc_program *prog, unsigned int bufsize, int npools,
>  			GFP_KERNEL);
>  	if (!serv->sv_pools) {
>  		kfree(serv);
> -		return NULL;
> +		goto out_err;
>  	}
>  
>  	for (i = 0; i < serv->sv_nrpools; i++) {
> @@ -423,6 +426,10 @@ __svc_create(struct svc_program *prog, unsigned int bufsize, int npools,
>  	svc_unregister(serv);
>  
>  	return serv;
> +
> +out_err:
> +	rpcb_put_local(); 
> +	return NULL;
>  }
>  
>  struct svc_serv *
> @@ -491,6 +498,8 @@ svc_destroy(struct svc_serv *serv)
>  	svc_unregister(serv);
>  	kfree(serv->sv_pools);
>  	kfree(serv);
> +
> +	rpcb_put_local();
>  }
>  EXPORT_SYMBOL_GPL(svc_destroy);
>  
> 

I don't get it -- what's the advantage of creating rpcbind clients in
__svc_create vs. the old way of creating them just before we plan to
use them?

With this scheme, won't we end up creating rpcbind sockets even when we
don't need them? For instance, if I create a callback socket for NFSv4
then I don't really need to talk to rpcbind. With this patch I'll still
get the rpcbind clients created though.

It would seem to me to make more sense to create the rpcbind clients
somewhere closer to svc_setup_socket, and only if SVC_SOCK_ANONYMOUS is
not set.

-- 
Jeff Layton <jlayton@...hat.com>
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