[libvirt] [PATCH 1/2] storage: Fix autostart of pool with "fc_host" type adapter

[Osier Yang]

On 07/01/14 01:21, John Ferlan wrote:
>
> On 01/06/2014 05:19 AM, Osier Yang wrote:
>> The "checkPool" is a bit different for pool with "fc_host"
>> type source adapter, since the vHBA it's based on might be
>> not created yet (it's created by "startPool", which is
>> involked after "checkPool" in storageDriverAutostart). So it
>> should not fail, otherwise the "autostart" of the pool will
>> fail either.
>>
>> The problem is easy to reproduce:
>>      * Enable "autostart" for the pool
>>      * Restart libvirtd service
>>      * Check the pool's state
>> ---
>>   src/storage/storage_backend_scsi.c | 14 ++++++++++++--
>>   1 file changed, 12 insertions(+), 2 deletions(-)
>>
> Not sure this is the right thing to do. With this change it doesn't
> matter what getAdapterName() returns for fc_host's...

It matters with if "*isActive" is true or false in the end. We don't
need to try to start the pool if it's already active.

>
> The getAdapterName() already has some code to specifically handle
> VIR_STORAGE_POOL_SOURCE_ADAPTER_TYPE_FC_HOST. The call to
> virGetFCHostNameByWWN() is similar to createVport() which is called by
> the 'start' path, except that the createVport() path will be happy if
> the name already exists.
>
> Since it seems the checkPool is meant to initialize things (from reading
> the error message in the calling function), why not create the vPort in
> the check function? It's a bit more refactoring that perhaps initially
> desired, although having a vport hanging around unused may not be quite
> right either.

No, "checkPool" is only involked when autostarting the pools. Not
by poolCreate, poolCreateXML, etc.  That's why creating pool must
fall into "startPool".

>
> Another option would be to have the check function perform "enough
> initialization" or "checks" to make it more likely that the start path
> will succeed.

That's actually what "checkPool" *should* do. But for "fc_host" pool,
it's a bit special, since it's unlike other pool types, the underlying
physical stuffs must be already existing on host.

>
> Looking at the code does cause me to wonder what happens in the
> "existing" code if the vport was created when the CheckPool function was
> called returning the NameByWWN() in the 'name' field. The subsequent
> getHostNumber() call uses the 'name' instead of what the start path does
> using the parent value.

It's right. "getHostNumber" in "checkPool" is to get the SCSI host
number of the vHBA. And then checking if the SCSI device shows
up in the sysfs tree with the got host number.

"getHostNumber" in "startPool" should get the parent's host number,
since it should know the sys file path "/.../.../create_vport". And write
command to it.

> It seems the "check" for fc_host and non-fc_host is different enough
> that the distinguishment needs to be in the check routine rather than
> hidden in the getAdapterName() function.

Not quite clear about your meaning. But getAdapterName is just
a wrapper to get the adapter name with regarding to different
adapter type. Any relationship of the "check" difference ?

Regards,
Osier