# Re: \[PATCH v5 9/9\] btrfs: btrfs\_copy\_file\_range() only supports reflinks

- From: Christoph Hellwig \<hidden\>
- Date: 2015-10-16 12:25:44 
- List: linux-api
- Page: https://ratatoskr.run/linux-api/2015/10/100691
- Thread: https://ratatoskr.run/linux-api/2015/10/100691/t.md

```text
On Fri, Oct 16, 2015 at 07:49:19AM -0400, Chris Mason wrote:
> > Yes, that would be my preference.  I'd also like to understand what
> > exactly btrfs does in fallocate.
> 
> For which part?  The answer changes based on how many references there
> are to a given fallocated region.

Both cases.  With btrfs allocating new block on every write how do you
avoid that ENOSPC?  Is there a unassigned block preallocation that's
made persistent in some way?
```