Re: [Qemu-devel] [PATCH 1/7] block: only force IO completion in .bdrv_truncate if we are shrinking

[Kevin Wolf]

Am 08.03.2013 um 12:46 hat Peter Lieven geschrieben:
> 
> Am 08.03.2013 um 10:35 schrieb Kevin Wolf <address@hidden>:
> 
> > Am 08.03.2013 um 10:23 hat Paolo Bonzini geschrieben:
> >> Il 08/03/2013 08:53, Peter Lieven ha scritto:
> >>>> 
> >>>> I think the fix is to only call it for the monitor command.  Optionally,
> >>>> when shrinking, assert that there are no requests in flight.
> >>> 
> >>> Okay.
> >>> 
> >>> What is the plan? just fix this or fix the whole thing (which seems to
> >>> be some
> >>> work).
> >>> 
> >>> The suggested patch from Jeff will break iscsi_truncate as bs->growable
> >>> is 1 currently.
> >> 
> >> I guess it's up to Kevin and Jeff.
> > 
> > Someone needs to send a fix for the qcow1 (and probably vmdk)
> > regression, otherwise I'll have to revert the patch.
> 
> What about Paolos suggestion to call bdrv_drain_all() from the block_resize
> command and not in bdrv_truncate? It is not a the complete solution, but it
> will fix the regression. However, what happens if someone resizes a qcow2
> device?

I suppose you mean qcow1? It doesn't support resizing images, but even
if it did, this shouldn't be a problem: The problematic case is the call
of bdrv_drain_all() during a read/write function, which would have to
wait for itself to complete. As soon as you restrict the
bdrv_drain_all() to the monitor, waiting for in-flight I/Os should just
work.

Kevin