# Re: \[PATCH 1/2\] man2: document FICLONE and FICLONERANGE

- From: Darrick J. Wong \<hidden\>
- Date: 2016-01-28 19:18:46 
- List: linux-api
- Page: https://ratatoskr.run/linux-api/2016/01/102968
- Thread: https://ratatoskr.run/linux-fsdevel/2015/12/102483/t.md

```text
On Thu, Jan 28, 2016 at 05:33:29AM -0800, Christoph Hellwig wrote:
> Now that we have this in 4.5-rc1 let's get this into man-pages as well.
> 
> > --- /dev/null
> > +++ b/man2/ioctl_ficlone.2
> 
> think this should be a link to the clone range man page, and the
> both ioctls should be documented together.  Basically just document
> FICLONERANGE and then mentiond that FICLONE does a whole file clone.

Ok, that's an easy switch to make.

> > +.B #include <sys/ioctl.h>
> 
> Don't we need uapi/linux/fs.h as well?

Err... yes. :)

> > Not all filesystems support
> > +overlapping reflink ranges in the same file.
> 
> Which one doesn't?

At the moment, neither btrfs nor XFS support it.

I don't think it'd be difficult for XFS (make a copy of the extent mappings in
the source area, increase the refcounts of those blocks, do the usual
punch-and-remap, then delete & decrement that copy of the mappings) but that
can come later.

> Also there should be a sentence that the clones are atomic vs
> concurrent writes, so no locks need to be taken for a consistent
> snapshot.

<nod>

I've updated the manpages and will repush the patchset ... optimistically,
when XFS reflink RFCv5 comes out, but sooner if anyone requests it. :)

Thank you for the review!

--D

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