Re: loop-aes: It is not longer possible to create a filesystem on an encrypted DVD-RAM

Hi Jari!

Jari Ruusu wrote:

Thomas Siedlich wrote:

quoted

I try to format a loop-aes encrypted DVD-RAM in
/dev/sr0 with mke2fs.

What loop-AES version are you using?

3.3a, which is the latest in Debian.
I see sourceforge has 3.6b :-( and I see also that the Debian package
has orphaned.
<http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=614808>
It's a pity.

What kernel version are you using?

2.6.35.3 (selfcompiled from kernel.org).

quoted

,----[/var/log/syslog]
| Mar 27 15:29:27 eagle kernel: loop2:
loop_end_io_transfer err=-95 bi_rw=0x461

Backing device returned EOPNOTSUPP (Operation not supported
on transport
endpoint) error for a write. Interpreting rest of bi_rw
bits depends on
kernel version. For 2.6.38 kernel bi_rw means: "metadata io
request",
"request to discard sectors", and "This bio has already
been subjected to
throttling rules. Don't do it again"

For my kernel it should mean (if I interpret 
/usr/src/linux/include/linux/bio.h right):
"Tell the IO scheduler not to wait for more requests after this
        one has been submitted, even if it is a SYNC request."
"synchronous I/O hint."
"barrier"
"write"

quoted

| Mar 27 15:29:27 eagle kernel: Buffer I/O error on
  device loop2, logical block 0
| Mar 27 15:29:27 eagle kernel: lost page write due to
  I/O error on loop2

Somehow EOPNOTSUPP error got interpreted as I/O error
and/or write was not
retried with bi_rw bits cleared that backing device do not
support.

quoted

| Mar 27 15:29:27 eagle kernel: loop2:
  loop_end_io_transfer err=-95 bi_rw=0x20
| Mar 27 15:29:27 eagle kernel: Buffer I/O error on
  device loop2, logical block 0

Backing device returned EOPNOTSUPP error for a read.
Interpreting rest of
bi_rw bits depends on kernel version. For 2.6.38 kernel
bi_rw means:
"metadata io request".

Here:
"barrier"
and
"read"

So "barrier" is the same in both messages. But why does it work
without loop? The backing device should be the same, shouldn't it?

quoted

It just works fine but unencrypted :-(.

As a temporary workaround, you can create unencrypted file
system and then
encrypt it in-place using aespipe tool.

Great idea! I give it a try.

dd if=/dev/sr0 bs=64k | aespipe -e AES256 -K ./key.gpg \
  | dd of=/dev/sr0 bs=64k conv=notrunc

This works. Thanks Jari for this workaround!

Thomas