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On Fri, Mar 4, 2016 at 12:11 PM, Shinobu Kinjo <shinobu.kj at gmail.com> wrote:
> What are you facing?

In this particular instance, I'm dealing with a case where we may add
some metadata in ceph that will get updated by the driver, and I need
to know how I'm going to be called.  I need to know whether e.g. I can
expect that ensure_share will only be called once at a time per share,
or whether it might be called multiple times in parallel, resulting in
a need for me to do more synchronisation a lower level.

This is more complicated than locking, because where we update more
than one thing at a time we also have to deal with recovery (e.g.
manila crashed halfway through updating something in ceph and now I'm
recovering it), especially whether the places we do recovery will be
called concurrently or not.

My very favourite answer here would be a pointer to some
documentation, but I'm guessing much this stuff is still at a "word of
mouth" stage.

John

> On Fri, Mar 4, 2016 at 9:06 PM, John Spray <jspray at redhat.com> wrote:
>> Hi,
>>
>> What expectations should driver authors have about multiple instances
>> of the driver being instantiated within different instances of
>> manila-share?
>>
>> For example, should I assume that when one instance of a driver is
>> having ensure_share called during startup, another instance of the
>> driver might be going through the same process on the same share at
>> the same time?  Are there any rules at all?
>>
>> Thanks,
>> John
>>
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