Re: reflink utils

Hi,

> Hi,
> 
> I've created some tools to work with reflinks (FICLONERANGE) which I'd
> like to include in the util-linux project.
> 
> Reflinks can be used to share equal blocks between files. Cloning a
> block using reflinks will not copy any data saving I/O and disk wear/
> space.
> 
> First tool is blkdiff which takes two files, a base file and a new file. 
> Then it creates both a delta file and an index, the delta file contains
> the different blocks in new file compared to the base file and an index
> file which contains the block indexes in either the base file or the
> delta file so the new file can be constructed from that.
> 
> This is a bit similar to rdiff from librsync but uses fixed block sizes
> and doesn't require the chunks to be in the same order. FICLONERANGE
> only allows you to clone blocks of the filesystems block size.
> 
> The next tool is blkpatch which uses the base, index and delta file to
> construct new file using reflinks.
> 
> I've also created blkcat which concatenates the blocks from all supplied
> files using reflinks into a single file with the idea to use this as a
> basefile to deduplicate files on a filesystem.
> 
> I think reflinks, or at least FICLONERANGE is linux specific so
> util-linux would be a good fit. Reflinks are currently supported (AFAIK)
> for BtrFS and XFS.
> 
> I'd love to know:
> 
> - can/should I contribute these to util-linux?
> - are blkdiff, blkpatch and blkcat good names?
> - what's required more? I can image I need to add some man pages etc.

I have contributed to the util-linux project on multiple occasions.

I hope my commit 
https://github.com/util-linux/util-linux/pull/2627/commits/0d5f67b29ce487e9cfff7c8b16aa8f9e7c0e2d10
helps you. This may be one of the smallet commit that added a new
command to util-linux.

See also the commits added after the commit:
https://github.com/util-linux/util-linux/pulls?q=is%3Apr+is%3Aclosed+exch
They fixed my mistakes.

Masatake YAMATO