[Xen-devel] [BUG] domU hangs when mkfs over a cryptsetup mapped from a file lying on rootfs

["tVos" <tvos@xxxxxxx>]

Hello xen-developers,

i think i found a bug, so i report now everything i did and what happened
and what i expected below, and let you tell me if this bug is confirmed.

-----BEGIN BUG REPORT-----
Distro: Debian 7.1 Wheezy
XEN: xen-hypervisor-4.1-amd64          4.1.4-3+deb7u1
Kernel: 3.2.0-4-amd64 #1 SMP Debian 3.2.46-1 x86_64 GNU/Linux


First i created a new domU:
xen-create-image --hostname=testtest --ip=10.3.4.1 --arch=amd64
--dist=wheezy --size=30Gb --memory=256Mb --vcpus=1 --verbose --noswap
--dir=/media/xen

I startet it and got into console with:
xm create testtest.cfg && xm console testtest

I logged in and installed cryptsetup and gddrescue:
apt-get update && apt-get install cryptsetup gddrescue

I created a 10GB file from /dev/zero:
ddrescue -b 4096 -s 10G /dev/zero ./testvolume

Then I luksFormatet and mapped it:
cryptsetup luksFormat ./testvolume
cryptsetup luksOpen ./testvolume testvolume

*** Until here everything was normal and as expected. ***

Now i tried to mkfs the mapped crypted file:
mkfs -t ext3 /dev/mapper/testvolume

the mkfs.ext3 got until "Writing inode tables: 22/75" and got stuck there.
The domU hangsup in a way that it doesn't ract anymore. No deamon reacts,
getty don't react anymore, and sometimes the dmesg of the domU says, that
a process did hang more than 120sec.

xentop and xm list says the domU are in blocking mode, the other domUs
continue working normaly and the host also works normaly.

no messages concerning this in host dmesg nor in xen dmesg. Nothing in the
logfiles.

The only way to recover the domU is waiting a _very_ long period of time,
usually 12-48h then it suddenly continues and finish the mkfs.ext; or to
xm destroy the domU and create it again.

I tested this on my Xen setup as well as on other similar XEN setups, and
diferent parameters such like guestroofs on a file, or als volumegroup,
more or less RAM, more or less disk, more or less CPUs, with and without
swap.

All setups are standart debian setups out of the box.
-----END BUG REPORT----

Please tell me what more infos you need, i will try to provide it asap.
Also please tell me if i should try somthing or reconfigure something and
try this scenario again.

Assistance will be apreciated. Many thanks in advance.

Sincerely,
tVos

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