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>
diff --git a/net/sunrpc/rpcb_clnt.c b/net/sunrpc/rpcb_clnt.c
index b1f08bd..4f8af63 100644
--- a/net/sunrpc/rpcb_clnt.c
+++ b/net/sunrpc/rpcb_clnt.c
@@ -620,9 +620,10 @@
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 @@
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 @@
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 @@
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_nofree:
rpcb_wake_rpcbind_waiters(xprt, status);
task->tk_status = status;
+ xprt_put(xprt);
}
EXPORT_SYMBOL_GPL(rpcb_getport_async);