btrfs-clone-fail-output

gistfile1.txt

james@simba:~$ sudo bash -x ~/btrfs-clone-fail 
+ rm --force /btrfs-device /btrfs-filesystem
rm: cannot remove '/btrfs-filesystem': Is a directory
+ truncate --size 1GiB /btrfs-device
+ mkdir /btrfs-filesystem
mkdir: cannot create directory '/btrfs-filesystem': File exists
+ mkfs.btrfs /btrfs-device

WARNING! - Btrfs v3.12 IS EXPERIMENTAL
WARNING! - see http://btrfs.wiki.kernel.org before using

Turning ON incompat feature 'extref': increased hardlink limit per file to 65536
fs created label (null) on /btrfs-device
	nodesize 16384 leafsize 16384 sectorsize 4096 size 1.00GiB
Btrfs v3.12
+ mount /btrfs-device /btrfs-filesystem
+ btrfs subvolume create /btrfs-filesystem/source
Create subvolume '/btrfs-filesystem/source'
+ btrfs subvolume create /btrfs-filesystem/target
Create subvolume '/btrfs-filesystem/target'
+ touch /btrfs-filesystem/source/cow
+ touch /btrfs-filesystem/source/nocow
+ chattr +C /btrfs-filesystem/source/nocow
+ btrfs subvolume snapshot -r /btrfs-filesystem/source /btrfs-filesystem/snapshot
Create a readonly snapshot of '/btrfs-filesystem/source' in '/btrfs-filesystem/snapshot'
+ cp --reflink=always /btrfs-filesystem/snapshot/cow /btrfs-filesystem/target
+ cp --reflink=always /btrfs-filesystem/snapshot/nocow /btrfs-filesystem/target
cp: failed to clone '/btrfs-filesystem/target/nocow' from '/btrfs-filesystem/snapshot/nocow': Invalid argument