Implement the new Operations::timeout callback for rnull and return
TimeoutReturn::ResetTimer.

Using ResetTimer keeps the behavior close to the existing blk-mq
default timeout handling while proving that the Rust timeout
abstraction wires cleanly into a driver.

Signed-off-by: Wenzhao Liao <wenzhaoliao@ruc.edu.cn>
---
 drivers/block/rnull/rnull.rs | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/block/rnull/rnull.rs b/drivers/block/rnull/rnull.rs
index 0ca8715febe8..3833a5bec7a4 100644
--- a/drivers/block/rnull/rnull.rs
+++ b/drivers/block/rnull/rnull.rs
@@ -97,4 +97,8 @@ fn complete(rq: ARef<mq::Request<Self>>) {
             // point, and so `end_ok` cannot fail.
             .expect("Fatal error - expected to be able to end request");
     }
+
+    fn timeout(_rq: &mq::Request<Self>) -> mq::TimeoutReturn {
+        mq::TimeoutReturn::ResetTimer
+    }
 }
-- 
2.34.1