Re: [Qemu-devel] nbd: Possible regression in 2.9 RCs

[Ciprian Barbu]

I suspect the culprit here is [1]. I've started a git bisect between this 
commit and v2.8.0 and during this time I found similar erros 
"/root/qemu/nbd/server.c:nbd_receive_request():L706: read failed"

I suspect this fix tried to solve a bunch of these read fails, but broke write 
requests.

[1] https://github.com/qemu/qemu/commit/8a7ce4f9338c475df1afc12502af704e4300a3e0

From: address@hidden [mailto:address@hidden On Behalf Of Ciprian Barbu
Sent: Friday, March 31, 2017 7:04 PM
To: address@hidden; Eric Blake <address@hidden>; Alexandru Avadanii 
<address@hidden>
Cc: Jeff Cody <address@hidden>; Markus Armbruster <address@hidden>; svc-armband 
<address@hidden>
Subject: [Cosnos] [Qemu-devel] nbd: Possible regression in 2.9 RCs

Hello,

Similar to the other thread about possible regression with rbd, there might be 
a regression with nbd.
This time we are launching an instance from an image (not volume) and try to 
live migrate it:

nova live-migration <test_instance>

The nova-compute service complains with:

2017-03-31 15:32:56.179 7806 INFO nova.virt.libvirt.driver 
[req-15d79cbe-5956-4738-92df-3624e6b993ee d795de59fb9a4ea38776a11d20ae8469 
cee03e74881f4ccba3b83345fb652b2c - - -] [instance: 
6a04508f-5d79-4582-8e2c-4cc368753f6c] Migration running for 0 secs, memory 100% 
remaining; (bytes processed=0, remaining=0, total=0)
2017-03-31 15:32:58.029 7806 WARNING stevedore.named 
[req-73bc0113-5555-4dd8-8903-d3540cc61b47 b9fbceeadd2d4d1bab9c90ae104db1f7 
7e7db99b32c6467184701e9a0c2f1de7 - - -] Could not load instance_network_info
2017-03-31 15:32:59.038 7806 ERROR nova.virt.libvirt.driver 
[req-15d79cbe-5956-4738-92df-3624e6b993ee d795de59fb9a4ea38776a11d20ae8469 
cee03e74881f4ccba3b83345fb652b2c - - -] [instance: 
6a04508f-5d79-4582-8e2c-4cc368753f6c] Live Migration failure: internal error: 
unable to execute QEMU command 'nbd-server-add': Conflicts with use by 
drive-virtio-disk0 as 'root', which does not allow 'write' on #block143
2017-03-31 15:32:59.190 7806 ERROR nova.virt.libvirt.driver 
[req-15d79cbe-5956-4738-92df-3624e6b993ee d795de59fb9a4ea38776a11d20ae8469 
cee03e74881f4ccba3b83345fb652b2c - - -] [instance: 
6a04508f-5d79-4582-8e2c-4cc368753f6c] Migration operation has aborted

I will try and bisect it myself, but I thought I would paste this here first, 
just so you know there is this issue too.

Regards,
/Ciprian