From mboxrd@z Thu Jan  1 00:00:00 1970
From: Roman Kapusta <roman.kapusta@gmail.com>
Subject: performance of cp and mv between subvolumes
Date: Thu, 7 Oct 2010 11:57:02 +0200
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Shouldn't be possible to move or copy (COW) big files between two
subvolumes of one btrfs filesystem instantly - without real data
movement?

cp --reflink between subvolumes is returning error: cp: failed to
clone `...': Invalid cross-device link
mv between subvolumes is really slow - looks like it is moving all data

To circumvent this I can create new snapshot and then remove
everything except files I want to copy/move to this new subvolume and
I gained the same effect quite fast, but indirectly, is there some way
how to do it directly when subvolume already exists?

Roman Kapusta