SUNRPC: Fix races when closing the socket

Ensure that we bump the xprt->connect_cookie when we set the
XPRT_CLOSE_WAIT flag so that another call to
xprt_conditional_disconnect() won't race with the reconnection.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

net/sunrpc/xprt.c

@@ -735,6 +735,8 @@ static void xprt_autoclose(struct work_struct *work)
 	unsigned int pflags = memalloc_nofs_save();
 
 	trace_xprt_disconnect_auto(xprt);
+	xprt->connect_cookie++;
+	smp_mb__before_atomic();
 	clear_bit(XPRT_CLOSE_WAIT, &xprt->state);
 	xprt->ops->close(xprt);
 	xprt_release_write(xprt, NULL);

net/sunrpc/xprtsock.c

@@ -1134,6 +1134,7 @@ static void xs_run_error_worker(struct sock_xprt *transport, unsigned int nr)
 
 static void xs_sock_reset_connection_flags(struct rpc_xprt *xprt)
 {
+	xprt->connect_cookie++;
 	smp_mb__before_atomic();
 	clear_bit(XPRT_CLOSE_WAIT, &xprt->state);
 	clear_bit(XPRT_CLOSING, &xprt->state);