SEEK_HOLE and SEEK_DATA extensions for lseek?

[Pedro F. Giffuni]

Hi;

I suggested this some time ago to Matt in private but now that hammer 
seems to be gaining stability and completeness, it looks like a good 
time to suggest it in public.

It would be nice to have DragonflyBSD support the lseek(2) extensions 
originally proposed for ZFS almost 4 years ago:

http://blogs.sun.com/bonwick/entry/seek_hole_and_seek_data

These were adopted by FreeBSD and would make perfect sense to have in 
hammer.

At the time Matt was busy with bigger issues, but he expressed he would 
commit it if someone came up with patches (and hopefully test cases).

cheers,

Pedro.