Xen users - Nov 2007 - Problem to get more than 8 loopback deviceses.

On Sun, 17 Dec 2006, Madd Sauer wrote:

> localhost:/dev# grep loop /var/log/dmesg
> Kernel command line: root=/dev/sda1 ro console=tty0 max_loop=128
> loop: loaded (max 8 devices)

Hallo  Madd!

I have the same problem.
Did you  find a solution?

Which distri and version do you use?
# xm dmesg | grep version

I have perhaps a workaround.

regards T.

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Torsten lehmann
LauNOC


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Torsten Lehmann schrieb:
> On Sun, 17 Dec 2006, Madd Sauer wrote:
> 
> 
>> localhost:/dev# grep loop /var/log/dmesg
>> Kernel command line: root=/dev/sda1 ro console=tty0 max_loop=128
>> loop: loaded (max 8 devices)
> 
> 
> Hallo  Madd!
> 
> I have the same problem.
> Did you  find a solution?
> 
> Which distri and version do you use?
> # xm dmesg | grep version
> 
> I have perhaps a workaround.
Adding netloop.nloopbacks=16 should help.

For grub for example, this would look like below:

title Xen
   kernel /boot/xen-3.1.gz dom0_mem=256M
   module /boot/vmlinuz-2.6.18-xen root=/dev/md1 netloop.nloopbacks=16 
xencons=off
   module /boot/initrd-2.6.18-xen.img




-- 
Tomasz Chmielewski
http://lists.wpkg.org



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On Tue, 13 Nov 2007, Tomasz Chmielewski wrote:
> >
> >> localhost:/dev# grep loop /var/log/dmesg
> >> Kernel command line: root=/dev/sda1 ro console=tty0 max_loop=128
> >> loop: loaded (max 8 devices)
> >
>
> Adding netloop.nloopbacks=16 should help.
>
> For grub for example, this would look like below:
>
> title Xen
>    kernel /boot/xen-3.1.gz dom0_mem=256M
>    module /boot/vmlinuz-2.6.18-xen root=/dev/md1 netloop.nloopbacks=16
> xencons=off
>    module /boot/initrd-2.6.18-xen.img
I did not test it.
Grub: "module ....max_loop=16" was always sufficient.

It does not seem to be Xen-problem:

-------------------------
  - lt. [1] max_loop setzen

# echo "options loop max_loop=16" >> /etc/modules.conf
# rmmod loop
# modprobe loop
loop: loaded (max 8 devices)

    -> option wird ignoriert!

-------------------------
  - test modprobe+option

# modprobe loop max_loop=16
loop: loaded (max 16 devices)

    - na geht doch...

-------------------------

# modinfo loop
filename:       /lib/modules/2.6.16.29-xen0/kernel/drivers/block/loop.ko
license:        GPL
alias:          block-major-7-*
vermagic:       2.6.16.29-xen0 PENTIUMIII gcc-3.3
depends:
parm:           max_loop:Maximum number of loop devices (1-256) (int)

# apt-cache show modutils | grep Version
Version: 2.4.26-1.2

# xm dmesg | egrep "version|ChangeSet"
 Xen version 3.0-unstable (root@xxx.de) (gcc version 3.3.5
(Debian 1:
3.3.5-13)) Fri Dec  8 08:11:00 CET 2006
 Latest ChangeSet: Wed Sep 27 14:30:36 2006 +0100 11633:000aa9510e55

# uname -r
2.6.16.29-xen0

  - Yes. very old...


It is not for me a problem. Article for information only...

--
Torsten lehmann
LauNOC


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hallo Tomasz!


Now i tested option "netloop.nloopbacks=16", but
problem not resolved. (modutils-2.4.26-1.2, 2.4.27.0-6)
(s. test netloop.nloopbacks)

What can i do?



Addition i send a note "node != max_loop".
(s. note_xen_loop-dev)


regards Torsten


-------------------------------------------------------------------------------
  - test netloop.nloopbacks
    (s. [3])

# dmesg | grep loop
Kernel command line: root=/dev/sda1 ro netloop.nloopbacks=16 xencons=off
max_loop=16
loop: loaded (max 8 devices)

# grep max_loop /etc/modules.conf
options loop max_loop=16

# modprobe -V
module-init-tools version 3.3-pre2

# apt-cache show modutils | grep Version
Version: 2.4.27.0-6

# apt-cache show module-init-tools | grep Version
Version: 3.3-pre4-2

# grep BLK_DEV_LOOP .config
CONFIG_BLK_DEV_LOOP=m
## (compiled as modul to better testing)

-------------------------------------------------------------------------------
- note_xen_loop-dev
  - zu log_xen_hotplug

  - xen liest die Devices nach folgenden Prinzip aus:

    loops=`ls /dev/loop*`
    -> 0 1 10 2 ...   -> crash dev #3 if (max_loop=8)

  -> d.h. Es duerfen nicht mehr Nodes existieren
          wie mit max_loop definiert!
          May exist no more Nodes, as loop-devices real exist.

-------------------------------------------------------------------------------



--
Torsten lehmann
LauNOC

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