can't start domU after resizing zfs volume

[Michael Reifenberger]

Zitat von Roger Pau Monné <roger.pau at citrix.com>:

> El 18/09/15 a les 19.41, Michael Reifenberger ha escrit:
>> Hi,
>> today I've got my first real xen dom0 error so far:
>>
>> I had a 20G zfs volume with windows installed (Windows has the PV
>> drivers installed).
>> The disk section of the cfg looks like:
>> ...
>> disk =  [
>>         '/dev/zvol/zdata/VM/win81/root,raw,hda,rw',
>>         '/VM/ISO/W81.PRO.X64.MULTi8.ESD.Apr2015.iso,raw,hdc:cdrom,r'
>>         ]
>> boot="d"
>> ...
>>
>>
>> This works until shutting down the domU and extending the volume (from
>> 20G) to 40G:
>>
>> zfs set volsize=40G zdata/VM/win81/root
>>
>> Now trying to start the guest I get:
>>
>> (vm)(root) # xl create win81.cfg
>> Parsing config from win81.cfg
>> libxl: error: libxl_device.c:950:device_backend_callback: unable to add
>> device with path /local/domain/0/backend/vbd/6/768
>> libxl: error: libxl_device.c:950:device_backend_callback: unable to add
>> device with path /local/domain/0/backend/vbd/6/5632
>> libxl: error: libxl_create.c:1153:domcreate_launch_dm: unable to add
>> disk devices
>> libxl: error: libxl_dm.c:1595:kill_device_model: unable to find device
>> model pid in /local/domain/6/image/device-model-pid
>> libxl: error: libxl.c:1608:libxl__destroy_domid:
>> libxl__destroy_device_model failed for 6
>> libxl: error: libxl_device.c:950:device_backend_callback: unable to
>> remove device with path /local/domain/0/backend/vbd/6/768
>> libxl: error: libxl_device.c:950:device_backend_callback: unable to
>> remove device with path /local/domain/0/backend/vbd/6/5632
>> libxl: error: libxl.c:1645:devices_destroy_cb: libxl__devices_destroy
>> failed for 6
>> libxl: info: libxl.c:1691:devices_destroy_cb: forked pid 2306 for
>> destroy of domain 6
>>
>> Since I saw in syslog that GEOM did some auto-moddings of the disk I did:
>>
>> `gpart commit zvol/zdata/VM/win81/root` on the dom0,
>> and `gpart resize -i 2 zvol/zdata/VM/win81/root`
>> but this didn't change the above failure.
>
> The handbook for bhyve when using ZVOLs is to create them using:
>
> # zfs create -V16G -o volmode=dev zroot/linuxdisk0
>
> Note the volmode=dev, which prevents GEOM from sniffing the partition table.
>

Thats at least a workaround!
Sometimes it would be nice to be able to access/pre-fill domU  
slices/partitions on
dom0 as well...

>> Only after reboot the guest can be started so somewhere must be a
>> mismatch of cached data...
>>
>> Any clues?
>
> This is from my own experience, but xen-blkback doesn't recover from
> errors sometimes and ends up in some kind of locked state waiting for a
> device to disconnect. Not sure if that's the case here, but I won't be
> surprised.

How does xen-blkback construct this Path: /local/domain/0/backend/vbd/6/768 or
/local/domain/0/backend/vbd/6/5632?

Is the volmode=dev changable after creation or only at creation time?


BTW: Many thanks for supporting XEN-dom0 under FreeBSD/ZFS.
So far it works surprisingly stable (Except some minor glitches like  
the above) :-)

Thanks!

Greetings
---
Michael


Gruß
---
Michael Reifenberger