Fallback to previous keepalive mechanism during failure

[Liryna]

Here in case of failure

dokany/dokan/dokan.c

Lines 282 to 299 in f32e1f0

	wchar_t keepalive_path[128];
	StringCbPrintfW(keepalive_path, sizeof(keepalive_path), L"\\\\?%s%s",
	instance->DeviceName, DOKAN_KEEPALIVE_FILE_NAME);
	HANDLE keepalive_handle =
	CreateFile(keepalive_path, GENERIC_READ, 0, NULL, OPEN_EXISTING, 0, NULL);
	if (keepalive_handle == INVALID_HANDLE_VALUE) {
	// We don't consider this a fatal error because the keepalive handle is only
	// needed for abnormal termination cases anyway.
	DbgPrintW(L"Failed to open keepalive file: %s\n", keepalive_path);
	}
	DWORD keepalive_bytes_returned = 0;
	BOOL keepalive_active =
	DeviceIoControl(keepalive_handle, FSCTL_ACTIVATE_KEEPALIVE, NULL, 0, NULL,
	0, &keepalive_bytes_returned, NULL);
	if (!keepalive_active) {
	DbgPrintW(L"Failed to activate keepalive handle.\n");
	}

we should fallback to previous keepalive mechanism. It is possible the failure happened when an older kernel without the keepalive file feature is used.

The commit that need to be partially revert:

1fdf9fb

[Liryna]

Done 6e68efb