Re: Supporting reflinked/cow files in coreutils

[Jeff liu]

FYI, I once implemented a similar patch to teach du(1) to show the disk footprint with reflinked stuff for OCFS2 only.

It is make use of rb-tree to figure out the shared extents and calculate the exactly used space eventually.

http://oss.oracle.com/pipermail/ocfs2-devel/2010-September/007293.html

http://oss.oracle.com/pipermail/ocfs2-devel/2010-September/007288.html

http://oss.oracle.com/pipermail/ocfs2-devel/2010-September/007287.html

I have not submit the patch set to Coreutils since I guess it is hard to accept by upstream as reflink and FIEMAP_EXTENT_SHARED flag are not spread over the general filesystems.

Thanks,

-Jeff

* Pádraig Brady (address@hidden) [20110414 17:30]:

I don't think there is anything else you could do,

like minimizing reads from a set of files with

shared extents, as there is no way to ID the extent.

Oh I suppose you could by using device_id, physical_offset.

You could extend the di_set stuff we have for matching

hardlinks to do that I suppose. But then one can currently

only clone a file, not an extent (on BTRFS at least).

What is your use case exactly?

As far as I understood the request, it's for reflink support in du so that
it's possible to see the space savings reflinks give you. Given your hint
I'll have a look at the di_set stuff to see how this can possibly be
extended to use the FIEMAP info.

Also it would be better to send details to address@hidden

as others might have suggestions.

Which I'm doing hereby. BTW, could somebody point me to the documents for
copyright assignment? I have one on file for GCC but now I'd need one for
coreutils.

Philpp