Online defragging of encrypted files is not currently implemented.
However, the move extent ioctl can still return successfully when
called.  For example, this occurs when xfstest ext4/020 is run on an
encrypted file system, resulting in a corrupted test file and a
corresponding test failure.

Until the proper functionality is implemented, fail the move extent
ioctl if either the original or donor file is encrypted.

Cc: stable@vger.kernel.org
Signed-off-by: NEric Whitney <enwlinux@gmail.com>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>