Re: [Qemu-block] [PATCH v3 0/2] block: allow flush on devices with open tray

[John Snow]

On 09/16/2016 04:33 AM, Kevin Wolf wrote:
> Am 16.09.2016 um 01:42 hat John Snow geschrieben:
> > One more try.
> >
> > The move to blk_flush altered the behavior of migration and flushing
> > nodes that are not reachable via the guest, but are still reachable
> > via QEMU and may or may not need to be flushed.
> >
> > This is likely the simplest solution for now until we nail down our
> > policy a bit more.
> >
> > This is intended for 2.6.2 and/or 2.7.1, to fix problems with libvirt
> > et al being unable to migrate QEMU when the CDROM tray is open.
> >
> > v3:
> >  Trying to take a hint from Kevin, reinstating bdrv_flush_all.
> >  If it's not what we want, we can try moving back to v2,
> >  acknowledging that a nicer solution in the future:
> >  (A) Can skip flushing on devices that just don't need it, and
> >  (B) Optionally institutes some sort of flush-on-eject policy.
>
> Reviewed-by: Kevin Wolf <address@hidden>
>
> The only part that I'm not completely happy with are the commit messages
> because there is a theme of "bypassing checks" in there. That's not
> really what happens because the requests don't come from something
> attached to the BlockBackends in the first place, and it also completely
> ignores the case of BDSes that aren't currently attached to any BB and
> are fixed by these changes as well.

I see your point. I just meant to say that it bypasses the checks in 
contrast to the other interface, but yes, there's a reason we're 
removing the checks here.

> Anyway, that's a minor problem as long as the code is right.

Let's fix it up. I'll reply with a suggestion.

> Kevin

Thank you.