linux-kernel - Re: [PATCH v5 1/8] SUNRPC: introduce helpers for reference counted rpcbind clients

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Date:	Tue, 20 Sep 2011 17:49:27 +0400
From:	Stanislav Kinsbursky <skinsbursky@...allels.com>
To:	"Trond.Myklebust@...app.com" <Trond.Myklebust@...app.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>
Subject: Re: [PATCH v5 1/8] SUNRPC: introduce helpers for reference counted
 rpcbind clients

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 |   53 ++++++++++++++++++++++++++++++++++++++++++++++++
  1 files changed, 53 insertions(+), 0 deletions(-)

diff --git a/net/sunrpc/rpcb_clnt.c b/net/sunrpc/rpcb_clnt.c
index e45d2fb..5f4a406 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 +164,56 @@ 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;
+}
+
+static void rpcb_set_local(struct rpc_clnt *clnt, struct rpc_clnt *clnt4)
+{
+	/* Protected by rpcb_create_local_mutex */
+	rpcb_local_clnt = clnt;
+	rpcb_local_clnt4 = clnt4;
+	rpcb_users++;
+	dprintk("RPC:       created new rpcb local clients (rpcb_local_clnt: "
+			"%p, rpcb_local_clnt4: %p)\n", rpcb_local_clnt,
+			rpcb_local_clnt4);
+}
+
  /*
   * Returns zero on success, otherwise a negative errno value
   * is returned.
--
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