SUNRPC: Fix races between socket connection and destroy code

When we're destroying the socket transport, we need to ensure that
we cancel any existing delayed connection attempts, and order them
w.r.t. the call to xs_close().
Reported-by: N"Suzuki K. Poulose" <suzuki.poulose@arm.com>
Acked-by: NJeff Layton <jlayton@poochiereds.net>
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>

net/sunrpc/xprtsock.c

@@ -881,8 +881,11 @@ static void xs_xprt_free(struct rpc_xprt *xprt)
  */
 static void xs_destroy(struct rpc_xprt *xprt)
 {
+	struct sock_xprt *transport = container_of(xprt,
+			struct sock_xprt, xprt);
 	dprintk("RPC:       xs_destroy xprt %p\n", xprt);
 
+	cancel_delayed_work_sync(&transport->connect_worker);
 	xs_close(xprt);
 	xs_xprt_free(xprt);
 	module_put(THIS_MODULE);