Re: [Qemu-devel] [PATCH 2/3] block: tell drivers about an image resize

[Christoph Hellwig]

> Do we want to check to ensure the size_changed flag isn't set before
> doing a second resize event?  I'm wondering if the truncate takes
> $longtime and user gets impatient and issues a second resize command.
> How should we respond?  Ignore it?  queue it up? 

The truncate is synchronous and the monitor command won't return before
it's done.  The interfact might be a bit cleaner if we'd just pass the
reason for the change callback as another argument.  I'll do that for
the next respin.

> Is there any other path that invokes bdrv_truncate?  If so, do we want
> invoke the call back in those scenarios or only if the truncate is
> initiated from the monitor invocation?

Currently only the qemu-img and qemu-io tools invooke bdrv_truncate.
But if we grow new users we should always tell the driver/guest about it
so that it knows about the size change.