SUNRPC: introduce helpers for reference counted rpcbind clients

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@parallels.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 53 insertions, 0 deletions

diff --git a/net/sunrpc/rpcb_clnt.c b/net/sunrpc/rpcb_clnt.c
index f588b852d41c..78af56579fa1 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);
+        }
+}
+
+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;
+        smp_wmb(); 
+        rpcb_users = 1;
+        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.