SUNRPC: Create a helper function for accessing the rpc_clnt's xprt_switch

This function takes the necessary rcu read lock to dereference the
client's rpc_xprt_switch and bump the reference count so it doesn't
disappear underneath us before returning. This does mean that callers
are responsible for calling xprt_switch_put() on the returned object
when they are done with it.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index 8df944444e9b6ce996288874720896a910615362..0b2c4b5484f58a9bb5fafce70f58bd1e2b260110 100644 (file)
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -797,15 +797,24 @@ out_revert:
 }
 EXPORT_SYMBOL_GPL(rpc_switch_client_transport);
 
-static
-int _rpc_clnt_xprt_iter_init(struct rpc_clnt *clnt, struct rpc_xprt_iter *xpi,
-                            void func(struct rpc_xprt_iter *xpi, struct rpc_xprt_switch *xps))
+static struct rpc_xprt_switch *rpc_clnt_xprt_switch_get(struct rpc_clnt *clnt)
 {
        struct rpc_xprt_switch *xps;
 
        rcu_read_lock();
        xps = xprt_switch_get(rcu_dereference(clnt->cl_xpi.xpi_xpswitch));
        rcu_read_unlock();
+
+       return xps;
+}
+
+static
+int _rpc_clnt_xprt_iter_init(struct rpc_clnt *clnt, struct rpc_xprt_iter *xpi,
+                            void func(struct rpc_xprt_iter *xpi, struct rpc_xprt_switch *xps))
+{
+       struct rpc_xprt_switch *xps;
+
+       xps = rpc_clnt_xprt_switch_get(clnt);
        if (xps == NULL)
                return -EAGAIN;
        func(xpi, xps);
@@ -2206,9 +2215,7 @@ call_connect_status(struct rpc_task *task)
                        struct rpc_xprt *saved = task->tk_xprt;
                        struct rpc_xprt_switch *xps;
 
-                       rcu_read_lock();
-                       xps = xprt_switch_get(rcu_dereference(clnt->cl_xpi.xpi_xpswitch));
-                       rcu_read_unlock();
+                       xps = rpc_clnt_xprt_switch_get(clnt);
                        if (xps->xps_nxprts > 1) {
                                long value;
 
@@ -3251,22 +3258,23 @@ void rpc_clnt_xprt_set_online(struct rpc_clnt *clnt, struct rpc_xprt *xprt)
 {
        struct rpc_xprt_switch *xps;
 
-       rcu_read_lock();
-       xps = rcu_dereference(clnt->cl_xpi.xpi_xpswitch);
-       rcu_read_unlock();
+       xps = rpc_clnt_xprt_switch_get(clnt);
        xprt_set_online_locked(xprt, xps);
+       xprt_switch_put(xps);
 }
 
 void rpc_clnt_xprt_switch_add_xprt(struct rpc_clnt *clnt, struct rpc_xprt *xprt)
 {
+       struct rpc_xprt_switch *xps;
+
        if (rpc_clnt_xprt_switch_has_addr(clnt,
                (const struct sockaddr *)&xprt->addr)) {
                return rpc_clnt_xprt_set_online(clnt, xprt);
        }
-       rcu_read_lock();
-       rpc_xprt_switch_add_xprt(rcu_dereference(clnt->cl_xpi.xpi_xpswitch),
-                                xprt);
-       rcu_read_unlock();
+
+       xps = rpc_clnt_xprt_switch_get(clnt);
+       rpc_xprt_switch_add_xprt(xps, xprt);
+       xprt_switch_put(xps);
 }
 EXPORT_SYMBOL_GPL(rpc_clnt_xprt_switch_add_xprt);