On Fri, Aug 09, 2019 at 02:18:29PM -0400, Theodore Ts'o wrote: > For debugging reasons, it's useful to know the contents of the extent > cache. Since the extent cache contains much of what is in the fiemap > ioctl, extend the fiemap interface to return this information via some > ext4-specific flags. Nak. No weird fs specific fiemap flags that aren't even in the uapi header. Please provide your own debug only interface.