SUNRPC: Unset RPC_TASK_NO_RETRANS_TIMEOUT for NULL RPCs

In some rare failure modes, the server is actually reading the
transport, but then just dropping the requests on the floor.
TCP_USER_TIMEOUT cannot detect that case.

Prevent such a stuck server from pinning client resources
indefinitely by ensuring that certain idempotent requests
(such as NULL) can time out even if the connection is still
operational.

Otherwise rpc_bind_new_program(), gss_destroy_cred(), or
rpc_clnt_test_and_add_xprt() can wait forever.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index ca2000d8cf647739ff6f86c2befacb2661678836..d34737a8a68a86febad78b4025d2ba5afda0002e 100644 (file)
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -2694,6 +2694,18 @@ static const struct rpc_procinfo rpcproc_null = {
        .p_decode = rpcproc_decode_null,
 };
 
+static void
+rpc_null_call_prepare(struct rpc_task *task, void *data)
+{
+       task->tk_flags &= ~RPC_TASK_NO_RETRANS_TIMEOUT;
+       rpc_call_start(task);
+}
+
+static const struct rpc_call_ops rpc_null_ops = {
+       .rpc_call_prepare = rpc_null_call_prepare,
+       .rpc_call_done = rpc_default_callback,
+};
+
 static
 struct rpc_task *rpc_call_null_helper(struct rpc_clnt *clnt,
                struct rpc_xprt *xprt, struct rpc_cred *cred, int flags,
@@ -2707,7 +2719,7 @@ struct rpc_task *rpc_call_null_helper(struct rpc_clnt *clnt,
                .rpc_xprt = xprt,
                .rpc_message = &msg,
                .rpc_op_cred = cred,
-               .callback_ops = (ops != NULL) ? ops : &rpc_default_ops,
+               .callback_ops = ops ?: &rpc_null_ops,
                .callback_data = data,
                .flags = flags | RPC_TASK_SOFT | RPC_TASK_SOFTCONN |
                         RPC_TASK_NULLCREDS,
@@ -2758,6 +2770,7 @@ static void rpc_cb_add_xprt_release(void *calldata)
 }
 
 static const struct rpc_call_ops rpc_cb_add_xprt_call_ops = {
+       .rpc_call_prepare = rpc_null_call_prepare,
        .rpc_call_done = rpc_cb_add_xprt_done,
        .rpc_release = rpc_cb_add_xprt_release,
 };