Re: [PATCH v5 9/9] btrfs: btrfs_copy_file_range() only supports reflinks

On Sat, Oct 17, 2015 at 08:44:35AM +1100, Dave Chinner wrote:

quoted

When we're doing writes, it'll check the preallocated extents for extra
refs and force COW if any exist.  So writes into a preallocated region
can enospc.

This really seems like an btrfs interpretation/implementation
issue, not a problem for reflink in general.

Right, now matter how we do it there are tradeoffs, and this one seemed
the least surprising to me.  I don't think it's a big problem at all.

Automatically replacing preallocated extents with holes during clone
seems like a better compromise though (at least for btrfs anyway).

-chris