FWIW this is unreproducible as of kernel 3.2 rc2 so I guess this is squeeze only for cifs shares (as can be verified by running the test on a squeeze live CD). If there are other filesystems that might produce the same behaviour under some circumstances in current kernel I don't know. However, the close() man page clearly states that only doing fsync() you can be sure your file was closed successfully. Thanks Michal