FILE_SUPPORTS_SPARSE_FILES not set

[Christoph Hellwig]

On Thu, Aug 14, 2014 at 02:23:06PM -0700, Jeremy Allison wrote:
> > 
> > Yes, they do... but can they report back the sparse ranges??? Which is part of
> > the sparse support?
> 
> I think some filesystems have ioctls that
> can do that.

Use lseek SEEK_HOLE/SEEK_DATA or if you really have to the FIEMAP
ioctl.  The first also is portable to Solaris and maybe others by now.