test/bufferlist: ensure rebuild_aligned_size_and_memory() always rebuilds.

Before the patch the test case was showing an unreliable behaviour
dependent on the underlying memory allocator. It was because
the bufferlist rebuild can be skipped, resulting in unchanged number
of buffers, if all of them begin at aligned addresses.

The commit fixes that by allocating a 4 KiB-aligned buffer and
offsetting it by a small constant (42) to ensure the memory added
to the bufferlist begins at non-4 KiB address.

Signed-off-by: Radoslaw Zarzynski <rzarzyns@redhat.com>
(cherry picked from commit 88176acd27b0d495abf9396c7ae2c6ec3fa46b1b)

diff --git a/src/test/bufferlist.cc b/src/test/bufferlist.cc
index 1e3c765feebda1234ebdd5f0fc869371de2225e2..a610b8eb2f1a4363c069cc5e8a9005d010da7936 100644 (file)
--- a/src/test/bufferlist.cc
+++ b/src/test/bufferlist.cc
@@ -1737,13 +1737,14 @@ TEST(BufferList, rebuild_aligned_size_and_memory) {
      * scenario where the first bptr is both size and memory aligned and
      * the second is 0-length */
     bl.clear();
-    bufferptr ptr1(buffer::create_aligned(4096, 4096));
-    bl.append(ptr1);
-    bufferptr ptr(10);
-    /* bl.back().length() must be 0 */
-    bl.append(ptr, 0, 0);
+    bl.append(bufferptr{buffer::create_aligned(4096, 4096)});
+    bufferptr ptr(buffer::create_aligned(42, 4096));
+    /* bl.back().length() must be 0. offset set to 42 guarantees
+     * the entire list is unaligned. */
+    bl.append(ptr, 42, 0);
     EXPECT_EQ(bl.get_num_buffers(), 2);
     EXPECT_EQ(bl.back().length(), 0);
+    EXPECT_FALSE(bl.is_aligned(4096));
     /* rebuild_aligned() calls rebuild_aligned_size_and_memory().
      * we assume the rebuild always happens. */
     EXPECT_TRUE(bl.rebuild_aligned(4096));