drbd: rate limit an error message

If we don't rate limit it, and you happen to log err level messages via
serial console, an IO error on a disconnected Primary may cause serious
unresponsiveness.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
diff --git a/drivers/block/drbd/drbd_req.c b/drivers/block/drbd/drbd_req.c
index d26b213..31d04b1 100644
--- a/drivers/block/drbd/drbd_req.c
+++ b/drivers/block/drbd/drbd_req.c
@@ -813,7 +813,8 @@
 			     mdev->state.conn >= C_CONNECTED));
 
 	if (!(local || remote) && !is_susp(mdev->state)) {
-		dev_err(DEV, "IO ERROR: neither local nor remote disk\n");
+		if (__ratelimit(&drbd_ratelimit_state))
+			dev_err(DEV, "IO ERROR: neither local nor remote disk\n");
 		goto fail_free_complete;
 	}