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

From: Stanislav Kinsbursky <[email-masked]>
Date: Fri, 09 Sep 2011 20:41:56 +0400

09.09.2011 18:07, Jeff Layton пишет:
> On Fri, 09 Sep 2011 16:08:44 +0400
> Stanislav Kinsbursky<[email-masked]>  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<[email-masked]>
>>
>> ---
>>   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.

> 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.
>

Yep, you right. This is not a real problem from my pow.
But I'll think about how to avoid this creation for nfs callbacks.

> 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.
>

Probably. Will try to find better place.

-- 
Best regards,
Stanislav Kinsbursky