From 633a167ff04b1f9af6acde41f279c525b3ce87f3 Mon Sep 17 00:00:00 2001
From: Mykola Golub <mgolub@suse.com>
Date: Fri, 15 Mar 2019 15:17:42 +0000
Subject: [PATCH] librbd: when requeueing QOS throttled request queue it back

to preserve order of throttled requests, which is important for flush.

Signed-off-by: Mykola Golub <mgolub@suse.com>
---
 src/librbd/io/ImageRequestWQ.cc                | 2 +-
 src/test/librbd/io/test_mock_ImageRequestWQ.cc | 9 +++++----
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/src/librbd/io/ImageRequestWQ.cc b/src/librbd/io/ImageRequestWQ.cc
index a5101aa048438..70e6aae9c91c3 100644
--- a/src/librbd/io/ImageRequestWQ.cc
+++ b/src/librbd/io/ImageRequestWQ.cc
@@ -661,7 +661,7 @@ void ImageRequestWQ<I>::handle_throttle_ready(int r, ImageDispatchSpec<I> *item,
   ceph_assert(m_io_throttled.load() > 0);
   item->set_throttled(flag);
   if (item->were_all_throttled()) {
-    this->requeue_front(item);
+    this->requeue_back(item);
     --m_io_throttled;
     this->signal();
   }
diff --git a/src/test/librbd/io/test_mock_ImageRequestWQ.cc b/src/test/librbd/io/test_mock_ImageRequestWQ.cc
index 352b888d3996b..50daa83c777bc 100644
--- a/src/test/librbd/io/test_mock_ImageRequestWQ.cc
+++ b/src/test/librbd/io/test_mock_ImageRequestWQ.cc
@@ -105,6 +105,7 @@ struct ThreadPool::PointerWQ<librbd::io::ImageDispatchSpec<librbd::MockTestImage
 
   MOCK_METHOD0(front, ImageDispatchSpec*());
   MOCK_METHOD1(requeue_front, void(ImageDispatchSpec*));
+  MOCK_METHOD1(requeue_back, void(ImageDispatchSpec*));
 
   MOCK_METHOD0(dequeue, void*());
   MOCK_METHOD1(queue, void(ImageDispatchSpec*));
@@ -170,8 +171,8 @@ struct TestMockIoImageRequestWQ : public TestMockFixture {
     EXPECT_CALL(image_request_wq, queue(_));
   }
 
-  void expect_requeue_front(MockImageRequestWQ &image_request_wq) {
-    EXPECT_CALL(image_request_wq, requeue_front(_));
+  void expect_requeue_back(MockImageRequestWQ &image_request_wq) {
+    EXPECT_CALL(image_request_wq, requeue_back(_));
   }
 
   void expect_front(MockImageRequestWQ &image_request_wq,
@@ -425,7 +426,7 @@ TEST_F(TestMockIoImageRequestWQ, BPSQosNoBurst) {
   expect_tokens_requested(mock_queued_image_request, 2, true);
   expect_dequeue(mock_image_request_wq, &mock_queued_image_request);
   expect_all_throttled(mock_queued_image_request, true);
-  expect_requeue_front(mock_image_request_wq);
+  expect_requeue_back(mock_image_request_wq);
   expect_signal(mock_image_request_wq);
   ASSERT_TRUE(mock_image_request_wq.invoke_dequeue() == nullptr);
 }
@@ -449,7 +450,7 @@ TEST_F(TestMockIoImageRequestWQ, BPSQosWithBurst) {
   expect_tokens_requested(mock_queued_image_request, 2, true);
   expect_dequeue(mock_image_request_wq, &mock_queued_image_request);
   expect_all_throttled(mock_queued_image_request, true);
-  expect_requeue_front(mock_image_request_wq);
+  expect_requeue_back(mock_image_request_wq);
   expect_signal(mock_image_request_wq);
   ASSERT_TRUE(mock_image_request_wq.invoke_dequeue() == nullptr);
 }
-- 
2.39.5