Punching holes into (sparse) files - porting Solaris fcntl(F_FREESP) to FreeBSD?

[Attila Nagy]

  On 03/04/2011 05:39 PM, Adam Vande More wrote:
>
>
>     Is it possible to make regions of files, with already written data
>     sparse? (I'm interested to do this on ZFS)
>
>
>
> Well thereis sysutils/phantom
Thanks, but I don't want to rewrite the file. I thought that this is 
obvious from the other part of the e-mail, sorry.
So I would like to make existing, non-sparse regions sparse, without 
rewriting the file. This is what F_FREESP is for.