[dm-crypt] System hang during mkfs

[dm-crypt] System hang during mkfs

[Tim]

Hello,

I have run into a serious issue (system hang) while trying to create a
luks-based loopback disk.  I have reported this issue to Debian here:
  http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=729600

That should have most of the technical details you need to start.  I
suspect the behavior I'm seeing is very similar to this:
  http://www.saout.de/pipermail/dm-crypt/2012-July/002544.html

I am now running memtester on most of my VM's available memory and it
is now on loop #3 with no issues identified.

I'm really surprised to run across an issue like this under a stable
kernel, so any advice you could give on how to further debug this
would be greatly appreciated.

tim

Re: [dm-crypt] System hang during mkfs

[Milan Broz]

On 11/14/2013 10:29 PM, Tim wrote:
> Hello,
> 
> I have run into a serious issue (system hang) while trying to create a
> luks-based loopback disk.  I have reported this issue to Debian here:
>   http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=729600
> 
> That should have most of the technical details you need to start.  I
> suspect the behavior I'm seeing is very similar to this:
>   http://www.saout.de/pipermail/dm-crypt/2012-July/002544.html
> 
> I am now running memtester on most of my VM's available memory and it
> is now on loop #3 with no issues identified.
> 
> I'm really surprised to run across an issue like this under a stable
> kernel, so any advice you could give on how to further debug this
> would be greatly appreciated.

Well, the kernel Debian stable kernel, so it should be handled
really handled by the Debian distro bugzilla.
(Otherwise, please try more recent, ideally 3.12 stable kernel.
Using loop devices is quite common and I do not think there are recent
problems here.)

Also try use loop directly. Does mkfs works ok? What is the underlying
filesystem and mount parameters (on which image resides)?

If it "locks" paste kernel trace to bugzilla (through sysrq,
"echo t > /proc/sysrq-trigger" and see syslog.)

(It seems to me more like problem with loop device or combination
than with dmcrypt. Anyway, if you are able to reproduce it on upstream
kernel, add device mapper devel list to cc  - dm-devel@redhat.com)

Milan

Re: [dm-crypt] System hang during mkfs

[Tim]

> Well, the kernel Debian stable kernel, so it should be handled
> really handled by the Debian distro bugzilla.
> (Otherwise, please try more recent, ideally 3.12 stable kernel.
> Using loop devices is quite common and I do not think there are recent
> problems here.)

That's why I submitted it there.  But every single party that is
involved in kernel development or support likes to point the finger at
someone else without bothering to attempt reproducing.  That's been my
past experience, which is why I'm trying multiple avenues for support
here.
 
> Also try use loop directly. Does mkfs works ok? What is the underlying
> filesystem and mount parameters (on which image resides)?

Just tried a plain loopback device.  It is a tad slower than doing
mkfs directly on the file, but nothing close to the issues with the
luks loopback.


> If it "locks" paste kernel trace to bugzilla (through sysrq,
> "echo t > /proc/sysrq-trigger" and see syslog.)
> 
> (It seems to me more like problem with loop device or combination
> than with dmcrypt. Anyway, if you are able to reproduce it on upstream
> kernel, add device mapper devel list to cc  - dm-devel@redhat.com)

Yeah, that's where 99% of bug reporters stop...

tim