fix(test): verify block device IO after cross-kernel snapshot restore

guest_run_fio_iteration ran fio in the background and only checked that
the process launched, not that IO actually succeeded. Run fio in the
foreground with JSON output and assert that bytes were read from the
block device. This addresses the TODO about verifying the root device
is not corrupted after snapshot restore.

Signed-off-by: Jack Thomson <jackabt@amazon.com>

Author: JackThomson2

tests/framework/utils.py

@@ -555,13 +555,15 @@ def start_screen_process(screen_log, session_name, binary_path, binary_params):
 
 
 def guest_run_fio_iteration(ssh_connection, iteration):
-    """Start FIO workload into a microVM."""
-    fio = """fio --filename=/dev/vda --direct=1 --rw=randread --bs=4k \
-        --ioengine=libaio --iodepth=16 --runtime=10 --numjobs=4 --time_based \
-        --group_reporting --name=iops-test-job --eta-newline=1 --readonly \
-        --output /tmp/fio{} > /dev/null &""".format(iteration)
-    exit_code, _, stderr = ssh_connection.run(fio)
-    assert exit_code == 0, stderr
+    """Run FIO workload on a microVM and verify IO completed successfully."""
+    fio = (
+        "fio --filename=/dev/vda --direct=1 --rw=randread --bs=4k "
+        "--ioengine=libaio --iodepth=16 --runtime=10 --numjobs=4 --time_based "
+        "--group_reporting --name=iops-test-job --readonly --output-format=json"
+    )
+    _, stdout, _ = ssh_connection.check_output(fio)
+    total_read = json.loads(stdout)["jobs"][0]["read"]["io_bytes"]
+    assert total_read > 0, f"fio iteration {iteration}: no bytes read from block device"
 
 
 def check_filesystem(ssh_connection, disk_fmt, disk):

tests/integration_tests/functional/test_snapshot_restore_cross_kernel.py

@@ -72,7 +72,9 @@ def get_snapshot_dirs():
     snapshot_root_dir = Path(FC_WORKSPACE_DIR) / snapshot_root_name
     cpu_templates = ["None"] + get_supported_cpu_templates()
     for cpu_template in cpu_templates:
-        for snapshot_dir in snapshot_root_dir.glob(f"**/*_{cpu_template}_guest_snapshot"):
+        for snapshot_dir in snapshot_root_dir.glob(
+            f"**/*_{cpu_template}_guest_snapshot"
+        ):
             assert snapshot_dir.is_dir()
             yield pytest.param(snapshot_dir, id=snapshot_dir.name)
 
@@ -120,9 +122,7 @@ def test_snap_restore_from_artifacts(
     logger.info("Testing vsock device...")
     check_vsock_device(vm, bin_vsock_path, test_fc_session_root_path, vm.ssh)
 
-    # Run fio on the guest.
-    # TODO: check the result of FIO or use fsck to check that the root device is
-    # not corrupted. No obvious errors will be returned here.
+    logger.info("Testing block device via fio...")
     guest_run_fio_iteration(vm.ssh, 0)
 
     vm.kill()