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

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Hi Jari!

Jari Ruusu wrote:
> Thomas Siedlich wrote:
> > 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).

> > ,----[/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"

> > | 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.
> 
> > | 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?

> > 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



      
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