SUNRPC: Add refcounting to the struct rpc_xprt

In a subsequent patch, this will allow the portmapper to take a reference
to the rpc_xprt for which it is updating the port number, fixing an Oops.

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

3 files changed, 32 insertions, 9 deletions

diff --git a/include/linux/sunrpc/xprt.h b/include/linux/sunrpc/xprt.h
index de4efea7c856..bdeba8538c71 100644
--- a/include/linux/sunrpc/xprt.h
+++ b/include/linux/sunrpc/xprt.h
@@ -12,6 +12,7 @@
 #include <linux/uio.h>
 #include <linux/socket.h>
 #include <linux/in.h>
+#include <linux/kref.h>
 #include <linux/sunrpc/sched.h>
 #include <linux/sunrpc/xdr.h>
 
@@ -129,6 +130,7 @@ struct rpc_xprt_ops {
 };
 
 struct rpc_xprt {
+        struct kref             kref;           /* Reference count */
         struct rpc_xprt_ops *   ops;            /* transport methods */
         struct socket *         sock;           /* BSD socket layer */
         struct sock *           inet;           /* INET layer */
@@ -248,7 +250,8 @@ int			xprt_adjust_timeout(struct rpc_rqst *req);
 void                    xprt_release_xprt(struct rpc_xprt *xprt, struct rpc_task *task);
 void                    xprt_release_xprt_cong(struct rpc_xprt *xprt, struct rpc_task *task);
 void                    xprt_release(struct rpc_task *task);
-int                     xprt_destroy(struct rpc_xprt *xprt);
+struct rpc_xprt *       xprt_get(struct rpc_xprt *xprt);
+void                    xprt_put(struct rpc_xprt *xprt);
 
 static inline u32 *xprt_skip_transport_header(struct rpc_xprt *xprt, u32 *p)
 {
diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index ceadb728f0da..084a0ad5c64e 100644
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -177,7 +177,7 @@ out_no_path:
                 kfree(clnt->cl_server);
         kfree(clnt);
 out_err:
-        xprt_destroy(xprt);
+        xprt_put(xprt);
 out_no_xprt:
         return ERR_PTR(err);
 }
@@ -261,6 +261,7 @@ rpc_clone_client(struct rpc_clnt *clnt)
         atomic_set(&new->cl_users, 0);
         new->cl_parent = clnt;
         atomic_inc(&clnt->cl_count);
+        new->cl_xprt = xprt_get(clnt->cl_xprt);
         /* Turn off autobind on clones */
         new->cl_autobind = 0;
         new->cl_oneshot = 0;
@@ -337,15 +338,12 @@ rpc_destroy_client(struct rpc_clnt *clnt)
                 rpc_rmdir(clnt->cl_dentry);
                 rpc_put_mount();
         }
-        if (clnt->cl_xprt) {
-                xprt_destroy(clnt->cl_xprt);
-                clnt->cl_xprt = NULL;
-        }
         if (clnt->cl_server != clnt->cl_inline_name)
                 kfree(clnt->cl_server);
 out_free:
         rpc_free_iostats(clnt->cl_metrics);
         clnt->cl_metrics = NULL;
+        xprt_put(clnt->cl_xprt);
         kfree(clnt);
         return 0;
 }
diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
index a85f82baefc1..1f786f68729d 100644
--- a/net/sunrpc/xprt.c
+++ b/net/sunrpc/xprt.c
@@ -926,6 +926,7 @@ struct rpc_xprt *xprt_create_transport(int proto, struct sockaddr *ap, size_t si
                 return ERR_PTR(result);
         }
 
+        kref_init(&xprt->kref);
         spin_lock_init(&xprt->transport_lock);
         spin_lock_init(&xprt->reserve_lock);
 
@@ -958,16 +959,37 @@ struct rpc_xprt *xprt_create_transport(int proto, struct sockaddr *ap, size_t si
 
 /**
  * xprt_destroy - destroy an RPC transport, killing off all requests.
- * @xprt: transport to destroy
+ * @kref: kref for the transport to destroy
  *
  */
-int xprt_destroy(struct rpc_xprt *xprt)
+static void xprt_destroy(struct kref *kref)
 {
+        struct rpc_xprt *xprt = container_of(kref, struct rpc_xprt, kref);
+
         dprintk("RPC:      destroying transport %p\n", xprt);
         xprt->shutdown = 1;
         del_timer_sync(&xprt->timer);
         xprt->ops->destroy(xprt);
         kfree(xprt);
+}
 
-        return 0;
+/**
+ * xprt_put - release a reference to an RPC transport.
+ * @xprt: pointer to the transport
+ *
+ */
+void xprt_put(struct rpc_xprt *xprt)
+{
+        kref_put(&xprt->kref, xprt_destroy);
+}
+
+/**
+ * xprt_get - return a reference to an RPC transport.
+ * @xprt: pointer to the transport
+ *
+ */
+struct rpc_xprt *xprt_get(struct rpc_xprt *xprt)
+{
+        kref_get(&xprt->kref);
+        return xprt;
 }