test: add read balance mode test case

Signed-off-by: Zheng Yin <zhengyin@cmss.chinamobile.com>

qa/suites/rbd/qemu/features/readbalance.yaml

@@ -0,0 +1,11 @@
+overrides:
+  ceph:
+    conf:
+      client:
+        rbd read from replica policy: balance
+
+tasks:
+- exec:
+    osd.0:
+      - ceph osd require-osd-release octopus
+      - ceph osd set-require-min-compat-client octopus

src/test/librbd/mock/MockImageCtx.h

@@ -98,6 +98,7 @@ struct MockImageCtx {
       blkin_trace_all(image_ctx.blkin_trace_all),
       enable_alloc_hint(image_ctx.enable_alloc_hint),
       alloc_hint_flags(image_ctx.alloc_hint_flags),
+      read_flags(image_ctx.read_flags),
       ignore_migrating(image_ctx.ignore_migrating),
       enable_sparse_copyup(image_ctx.enable_sparse_copyup),
       mtime_update_interval(image_ctx.mtime_update_interval),
@@ -305,6 +306,7 @@ struct MockImageCtx {
   bool blkin_trace_all;
   bool enable_alloc_hint;
   uint32_t alloc_hint_flags;
+  uint32_t read_flags;
   bool ignore_migrating;
   bool enable_sparse_copyup;
   uint64_t mtime_update_interval;

src/test/librbd/test_librbd.cc

@@ -1948,6 +1948,7 @@ TEST_F(TestLibRBD, TestIO)
   uint64_t size = 2 << 20;  
 
   ASSERT_EQ(0, create_image(ioctx, name.c_str(), size, &order));
+  ASSERT_EQ(0, rados_conf_set(_cluster, "rbd_read_from_replica_policy", "balance"));
   ASSERT_EQ(0, rbd_open(ioctx, name.c_str(), &image, NULL));
   
   char test_data[TEST_IO_SIZE + 1];