SUNRPC: Use RCU to dereference the rpc_clnt.cl_xprt field

A migration event will replace the rpc_xprt used by an rpc_clnt.  To
ensure this can be done safely, all references to cl_xprt must now use
a form of rcu_dereference().

Special care is taken with rpc_peeraddr2str(), which returns a pointer
to memory whose lifetime is the same as the rpc_xprt.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
[ cel: fix lockdep splats and layering violations ]
[ cel: forward ported to 3.4 ]
[ cel: remove rpc_max_reqs(), add rpc_net_ns() ]
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 11 insertions, 4 deletions

diff --git a/net/sunrpc/rpcb_clnt.c b/net/sunrpc/rpcb_clnt.c
index b1f08bd67883..4f8af63798a2 100644
--- a/net/sunrpc/rpcb_clnt.c
+++ b/net/sunrpc/rpcb_clnt.c
@@ -620,9 +620,10 @@ static struct rpc_task *rpcb_call_async(struct rpc_clnt *rpcb_clnt, struct rpcbi
 static struct rpc_clnt *rpcb_find_transport_owner(struct rpc_clnt *clnt)
 {
         struct rpc_clnt *parent = clnt->cl_parent;
+        struct rpc_xprt *xprt = rcu_dereference(clnt->cl_xprt);
 
         while (parent != clnt) {
-                if (parent->cl_xprt != clnt->cl_xprt)
+                if (rcu_dereference(parent->cl_xprt) != xprt)
                         break;
                 if (clnt->cl_autobind)
                         break;
@@ -653,8 +654,12 @@ void rpcb_getport_async(struct rpc_task *task)
         size_t salen;
         int status;
 
-        clnt = rpcb_find_transport_owner(task->tk_client);
-        xprt = clnt->cl_xprt;
+        rcu_read_lock();
+        do {
+                clnt = rpcb_find_transport_owner(task->tk_client);
+                xprt = xprt_get(rcu_dereference(clnt->cl_xprt));
+        } while (xprt == NULL);
+        rcu_read_unlock();
 
         dprintk("RPC: %5u %s(%s, %u, %u, %d)\n",
                 task->tk_pid, __func__,
@@ -667,6 +672,7 @@ void rpcb_getport_async(struct rpc_task *task)
         if (xprt_test_and_set_binding(xprt)) {
                 dprintk("RPC: %5u %s: waiting for another binder\n",
                         task->tk_pid, __func__);
+                xprt_put(xprt);
                 return;
         }
 
@@ -734,7 +740,7 @@ void rpcb_getport_async(struct rpc_task *task)
         switch (bind_version) {
         case RPCBVERS_4:
         case RPCBVERS_3:
-                map->r_netid = rpc_peeraddr2str(clnt, RPC_DISPLAY_NETID);
+                map->r_netid = xprt->address_strings[RPC_DISPLAY_NETID];
                 map->r_addr = rpc_sockaddr2uaddr(sap, GFP_ATOMIC);
                 map->r_owner = "";
                 break;
@@ -763,6 +769,7 @@ bailout_release_client:
 bailout_nofree:
         rpcb_wake_rpcbind_waiters(xprt, status);
         task->tk_status = status;
+        xprt_put(xprt);
 }
 EXPORT_SYMBOL_GPL(rpcb_getport_async);