linux-kernel - Re: [PATCH v6 1/8] SUNRPC: introduce helpers for reference counted rpcbind clients

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Message-ID: <1319546750.2716.5.camel@lade.trondhjem.org>
Date:	Tue, 25 Oct 2011 14:45:50 +0200
From:	Trond Myklebust <Trond.Myklebust@...app.com>
To:	Stanislav Kinsbursky <skinsbursky@...allels.com>
Cc:	"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>,
	"devel@...nvz.org" <devel@...nvz.org>
Subject: Re: [PATCH v6 1/8] SUNRPC: introduce helpers for reference counted
 rpcbind clients

On Tue, 2011-10-25 at 16:41 +0400, Stanislav Kinsbursky wrote: 
> 25.10.2011 15:16, Trond Myklebust пишет:
> > On Tue, 2011-10-25 at 14:16 +0300, Stanislav Kinsbursky wrote:
> >> v6:
> >> 1) added write memory barrier to rpcb_set_local to make sure, that rpcbind
> >> clients become valid before rpcb_users assignment
> >> 2) explicitly set rpcb_users to 1 instead of incrementing it (looks clearer from
> >> my pow).
> >>
> >> v5: fixed races with rpcb_users in rpcb_get_local()
> >>
> >> This helpers will be used for dynamical creation and destruction of rpcbind
> >> clients.
> >> Variable rpcb_users is actually a counter of lauched RPC services. If rpcbind
> >> clients has been created already, then we just increase rpcb_users.
> >>
> >> Signed-off-by: Stanislav Kinsbursky<skinsbursky@...allels.com>
> >>
> >> ---
> >>   net/sunrpc/rpcb_clnt.c |   54 ++++++++++++++++++++++++++++++++++++++++++++++++
> >>   1 files changed, 54 insertions(+), 0 deletions(-)
> >>
> >> diff --git a/net/sunrpc/rpcb_clnt.c b/net/sunrpc/rpcb_clnt.c
> >> index e45d2fb..9fcdb42 100644
> >> --- a/net/sunrpc/rpcb_clnt.c
> >> +++ b/net/sunrpc/rpcb_clnt.c
> >> @@ -114,6 +114,9 @@ static struct rpc_program	rpcb_program;
> >>   static struct rpc_clnt *	rpcb_local_clnt;
> >>   static struct rpc_clnt *	rpcb_local_clnt4;
> >>
> >> +DEFINE_SPINLOCK(rpcb_clnt_lock);
> >> +unsigned int			rpcb_users;
> >> +
> >>   struct rpcbind_args {
> >>   	struct rpc_xprt *	r_xprt;
> >>
> >> @@ -161,6 +164,57 @@ static void rpcb_map_release(void *data)
> >>   	kfree(map);
> >>   }
> >>
> >> +static int rpcb_get_local(void)
> >> +{
> >> +	int cnt;
> >> +
> >> +	spin_lock(&rpcb_clnt_lock);
> >> +	if (rpcb_users)
> >> +		rpcb_users++;
> >> +	cnt = rpcb_users;
> >> +	spin_unlock(&rpcb_clnt_lock);
> >> +
> >> +	return cnt;
> >> +}
> >> +
> >> +void rpcb_put_local(void)
> >> +{
> >> +	struct rpc_clnt *clnt = rpcb_local_clnt;
> >> +	struct rpc_clnt *clnt4 = rpcb_local_clnt4;
> >> +	int shutdown;
> >> +
> >> +	spin_lock(&rpcb_clnt_lock);
> >> +	if (--rpcb_users == 0) {
> >> +		rpcb_local_clnt = NULL;
> >> +		rpcb_local_clnt4 = NULL;
> >> +	}
> >> +	shutdown = !rpcb_users;
> >> +	spin_unlock(&rpcb_clnt_lock);
> >> +
> >> +	if (shutdown) {
> >> +		/*
> >> +		 * cleanup_rpcb_clnt - remove xprtsock's sysctls, unregister
> >> +		 */
> >> +		if (clnt4)
> >> +			rpc_shutdown_client(clnt4);
> >> +		if (clnt)
> >> +			rpc_shutdown_client(clnt);
> >> +	}
> >> +	return;
> >
> > I'm removing this before applying...
> >
> Sorry, but I don't understand what exactly you are removing, and why?

The empty 'return' at the end of a void function: it is 100%
redundant...

-- 
Trond Myklebust
Linux NFS client maintainer

NetApp
Trond.Myklebust@...app.com
www.netapp.com

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