test/librbd: extend DiffIterateTest.DiffIterateDeterministic{,PP}

Currently we are laying data only at the beginning of an object.
Extend the skeletons to write to three different offsets in the middle
and also at the end of the object.

Separately, make C and C++ API test variants slightly different in
terms of offsets being targeted to not go through exactly the same
scenario twice.

Signed-off-by: Ilya Dryomov <[email protected]>

Author: idryomov

src/test/librbd/test_librbd.cc

@@ -7652,8 +7652,8 @@ class DiffIterateTest : public TestLibRBD {
 
   void test_deterministic_pp(librbd::Image& image, uint64_t object_off,
                              uint64_t len, uint64_t block_size) {
-    uint64_t off1 = 0 << 20;
-    uint64_t off2 = 4 << 20;
+    uint64_t off1 = 8 << 20;
+    uint64_t off2 = 16 << 20;
     uint64_t size = 20 << 20;
     uint64_t extent_len = round_up_to(object_off + len, block_size);
 
@@ -7876,14 +7876,22 @@ TYPED_TEST(DiffIterateTest, DiffIterateDeterministic)
 {
   REQUIRE(!is_feature_enabled(RBD_FEATURE_STRIPINGV2));
 
-  this->test_deterministic(0, 256);
+  EXPECT_NO_FATAL_FAILURE(this->test_deterministic(0, 256));
+  EXPECT_NO_FATAL_FAILURE(this->test_deterministic((1 << 20) - 256, 256));
+  EXPECT_NO_FATAL_FAILURE(this->test_deterministic((1 << 20) - 128, 256));
+  EXPECT_NO_FATAL_FAILURE(this->test_deterministic(1 << 20, 256));
+  EXPECT_NO_FATAL_FAILURE(this->test_deterministic((4 << 20) - 256, 256));
 }
 
 TYPED_TEST(DiffIterateTest, DiffIterateDeterministicPP)
 {
   REQUIRE(!is_feature_enabled(RBD_FEATURE_STRIPINGV2));
 
-  this->test_deterministic_pp(0, 256);
+  EXPECT_NO_FATAL_FAILURE(this->test_deterministic_pp(0, 2));
+  EXPECT_NO_FATAL_FAILURE(this->test_deterministic_pp((3 << 20) - 2, 2));
+  EXPECT_NO_FATAL_FAILURE(this->test_deterministic_pp((3 << 20) - 1, 2));
+  EXPECT_NO_FATAL_FAILURE(this->test_deterministic_pp(3 << 20, 2));
+  EXPECT_NO_FATAL_FAILURE(this->test_deterministic_pp((4 << 20) - 2, 2));
 }
 
 TYPED_TEST(DiffIterateTest, DiffIterateDiscard)