Add wal_sync_method=fdatasync for Windows.

Windows 10 gained support for flushing NTFS files with fdatasync()
semantics.  The main advantage over open_datasync (in Windows API terms
FILE_FLAG_WRITE_THROUGH) is that the latter does not flush SATA drive
caches.  The default setting is not changed, so users have to opt in to
this.

Discussion: https://postgr.es/m/CA%2BhUKGJZJVO%3DiX%2Beb-PXi2_XS9ZRqnn_4URh0NUQOwt6-_51xQ%40mail.gmail.com

1 files changed, 53 insertions, 0 deletions

diff --git a/src/port/fdatasync.c b/src/port/fdatasync.c
new file mode 100644
index 00000000000..afef853aa3c
--- /dev/null
+++ b/src/port/fdatasync.c
@@ -0,0 +1,53 @@
+/*-------------------------------------------------------------------------
+ *
+ * fdatasync.c
+ *	   Win32 fdatasync() replacement
+ *
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ *
+ * src/port/fdatasync.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#define UMDF_USING_NTSTATUS
+
+#ifdef FRONTEND
+#include "postgres_fe.h"
+#else
+#include "postgres.h"
+#endif
+
+#include "port/win32ntdll.h"
+
+int
+fdatasync(int fd)
+{
+	IO_STATUS_BLOCK iosb;
+	NTSTATUS	status;
+	HANDLE		handle;
+
+	handle = (HANDLE) _get_osfhandle(fd);
+	if (handle == INVALID_HANDLE_VALUE)
+	{
+		errno = EBADF;
+		return -1;
+	}
+
+	if (initialize_ntdll() < 0)
+		return -1;
+
+	memset(&iosb, 0, sizeof(iosb));
+	status = pg_NtFlushBuffersFileEx(handle,
+									 FLUSH_FLAGS_FILE_DATA_SYNC_ONLY,
+									 NULL,
+									 0,
+									 &iosb);
+
+	if (NT_SUCCESS(status))
+		return 0;
+
+	_dosmaperr(pg_RtlNtStatusToDosError(status));
+	return -1;
+}