Re: problem with device validation

Peter T. Breuer a écrit :
> "Also sprach denis bonnenfant:"
> 
>>I have a problem with nbd device validation before adding it to fr1 array :
>>
>>to be assembled, nbd device has to be validated. But i haven't found a reliable 
> 
> 
> I'm not sure I know what you mean by "validated".
> 
> If you mean the flag in the nbdinfo status line ...

yes
> 
> 
>>Device a:       Open
>>[a] State:      verify, rw, enabled, validated, show_errs, last error 0, lives 
> 
> 
> Then that's the ENBD_VALIDATED flag
> 
>      atomic_read (&lo->flags)
>            & ENBD_VALIDATED ? "validated, " : "",
> 
> which is set after a partition check has been done on the device, which
> is to say that sector zero has been read and parsed by the kernel.
> 
> If you have no reason to check for partitions, you can disable the
> check. It's a nuisance anyway, since there's a race in doing it - the
> kernel needs the partition layout to authorise accesses to minors,
> but we are talking through the minors via the daemons ... for that
> reason the damons fall back to talking through the whole disk device 
> using special auth codes if they can't talk through the minor devices.
> 
> You can disable the check by unsetting the ENBD_CHECK_PARTITIONS flag.
>
> That's the "check_partitions" flag in the status line. I see you don't
> have it set anyway, hence no partition check will be done. So I don't
> think the validated flag means anything.
> 
> Why are you interested in it?

in fact, the problem occurs in this situation :
- primary has been stopped.
- on secondary, enbd-client is running, but connection with server is lost
- raid is started on secondary with only the local disk.
- primary starts
- enbd-server is started on primary by init script. connexion is established 
with client.
- when i try to hotadd nbd device to secondary raid, sometimes it fails to read 
nbd superblock. I found that waiting nbd to be marked validated in nbdinfo 
solves the problem. But maybe it's a wrong diagnosis and there is a better way 
to be sure that enbd device is useable?