On 2/5/12 3:33 AM, Ron Yorston wrote:
> Eric Sandeen wrote:
>> Now that ext4, xfs, & ocfs2 can support punch hole, a tool to
>> "re-sparsify" a file by punching out ranges of 0s might be in order.
>> I'll see if util-linux wants it after it gets beat into shape.
>> (or did a tool like this already exist and I missed it?)
> Way ahead of you. I wrote my sparsify utility for ext2 in 2004:
Cool, I had not known about that one. But that one is a bit less generic -
ext2-specific and requiring an unmounted fs, right?
> It's mostly of historical interest now, I suppose. The sparsify utility
> doesn't work on ext4 and I long since gave up maintaining the kernel
> patch. I still use the zerofree utility, though.
> It would be nice to have a modern version of sparsify. I'll try it out.
Matthias' suggestion of adding SEEK_HOLE/SEEK_DATA makes very good sense too.
I should also untie the read/zero buffer size from the minimum hole size,
we should do optimal IO sizes regardless of the minimum hole size desired...