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

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Date:	Fri, 9 Sep 2011 15:01:04 -0400
From:	Jeff Layton <jlayton@...hat.com>
To:	Trond Myklebust <Trond.Myklebust@...app.com>
Cc:	Stanislav Kinsbursky <skinsbursky@...allels.com>,
	"linux-nfs@...r.kernel.org" <linux-nfs@...r.kernel.org>,
	Pavel Emelianov <xemul@...allels.com>,
	"neilb@...e.de" <neilb@...e.de>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"bfields@...ldses.org" <bfields@...ldses.org>,
	"davem@...emloft.net" <davem@...emloft.net>
Subject: Re: [PATCH v2 3/5] SUNRPC: make RPC service dependable on rpcbind
 clients creation

On Fri, 09 Sep 2011 14:44:34 -0400
Trond Myklebust <Trond.Myklebust@...app.com> wrote:

> On Fri, 2011-09-09 at 20:41 +0400, Stanislav Kinsbursky wrote: 
> > 09.09.2011 18:07, Jeff Layton пишет:
> > > 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?
> > >
> > 
> > The main problem here is not in creation, but in destroying those clients.
> > Now rpcbind clients are created during rpcb_register(). I.e. once per every family, program version and so on.
> > But can be unregistered for all protocol families by one call. So it's impossible to put reference counting for those clients in the place, where they are created now.
> 
> Could we perhaps set up a 'struct pernet_operations' to create a
> destructor for them?
> 

An even easier idea might be to just not take a reference to the
rpcbind client for svc_programs that have vs_hidden set on every
version.

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