Dear Maintainer,
I have the same problems like described, and found on archlinux that the
bug is fixed with kernel 3.17-2.
Source: https://wiki.archlinux.org/index.php/Snapper
Quotation:
*Warning: *
In kernels 3.17 and 3.17-1, snapper in combination with Btrfs
<https://wiki.archlinux.org/index.php/Btrfs> using read-only snapshots
will cause random corruption
<http://www.mail-archive.com/linux-btrfs@vger.kernel.org/msg38049.html>
and affected snapshots cannot be deleted without recreating the
filesystem. This bug is fixed as of 3.17-2.
