Files full of zeros with coreutils-8.11 and xfs (FIEMAP related?)

[Christoph Hellwig]

On Fri, Apr 15, 2011 at 11:24:19AM -0600, Eric Blake wrote:
> Would it be worth borrowing from Solaris' semantics and adding SEEK_HOLE
> and SEEK_DATA to lseek(2), as a higher level (less-detailed, but easier
> to define and easier to use) interface for discovering the regions of a
> file that only contain NUL bytes?

Yes, I've already suggested that both in this thread and on IRC.

For efficient copies it's the only usable interface.