Re: [Qemu-devel] [PATCH COLO-BLOCK v7 00/17] Block replication for continuous checkpoints

[Wen Congyang]

On 07/08/2015 12:56 AM, Michael R. Hines wrote:
> On 07/07/2015 04:23 AM, Paolo Bonzini wrote:
>>
>> On 07/07/2015 11:13, Dr. David Alan Gilbert wrote:
>>>>> This log is very stange. The NBD client connects to NBD server, and NBD 
>>>>> server wants to read data
>>>>> from NBD client, but reading fails. It seems that the connection is 
>>>>> closed unexpectedly. Can you
>>>>> give me more log and how do you use it?
>>> That was the same failure I was getting.   I think it's that the NBD server 
>>> and client are in different
>>> modes, with one of them expecting the export.
>> nbd_server_add always expects the export.
>>
>> Paolo
>>
> 
> OK, Wen, so your wiki finally does reflect this, but now we're back to the 
> "export not found error".
> 
> Again, here's the exact command line:
> 
> 1. First on the secondary VM:
> 
> qemu-system-x86_64 .........snip...........  -drive 
> if=none,driver=qcow2,file=foo.qcow2,id=mc1,cache=none,aio=native -drive 
> if=virtio,driver=replication,mode=secondary,throttling.bps-total-max=70000000,file.file.filename=active_disk.qcow2,file.driver=qcow2,file.backing.file.filename=hidden_disk.qcow2,file.backing.driver=qcow2,file.backing.allow-write-backing-file=on,file.backing.backing.backing_reference=mc1
> 
> 2. Then, then HMP commands:
> 
> nbd_server_start 0:6262
> nbd_server_add -w mc1
> 
> 3. Then the primary VM:
> 
> qemu-system-x86_64 .........snip...........  -drive 
> if=virtio,driver=quorum,read-pattern=fifo,no-connect=on,children.0.file.filename=bar.qcow2,children.0.driver=qcow2,children.1.file.driver=nbd,children.1.file.host=127.0.0.1,children.1.file.port=6262,children.1.driver=replication,children.1.mode=primary,children.1.ignore-errors=on
> 
> With the error: Server requires an export name
> 
> *but*, your wiki has no export name on the primary VM size, so I added the 
> export name back which is on your old wiki:
> 
> qemu-system-x86_64 .........snip...........  -drive 
> if=virtio,driver=quorum,read-pattern=fifo,no-connect=on,children.0.file.filename=bar.qcow2,children.0.driver=qcow2,children.1.file.driver=nbd,children.1.file.export=mc1,children.1.file.host=127.0.0.1,children.1.file.port=6262,children.1.driver=replication,children.1.mode=primary,children.1.ignore-errors=on:
>  Failed to read export length
> 

Hmm, I think you use v7 version. Is it right?
In this version, the correct useage for primary qemu is:
1. qemu-system-x86_64 .........snip...........  -drive 
if=virtio,driver=quorum,read-pattern=fifo,id=disk1,
                      
children.0.file.filename=bar.qcow2,children.0.driver=qcow2,

Then run hmp monitor command(It should be run after you run nbd_server_add in 
the secondary qemu):
child_add disk1 
child.driver=replication,child.mode=primary,child.file.host=127.0.0.1,child.file.port=6262,child.file.export=mc1,child.file.driver=nbd,child.ignore-errors=on

Thanks
Wen Congyang

> And server now says:
> 
> nbd.c:nbd_handle_export_name():L416: export not found
> nbd.c:nbd_send_negotiate():L562: option negotiation failed
> 
> .
>