[libvirt] [PATCH] Use unsigned timeout in cmdMigrateSetMaxDowntime

[Scott Garfinkle]

John Ferlan <jferlan at redhat.com> wrote on 07/10/2017 06:41:34 AM:

> From: John Ferlan <jferlan at redhat.com>
> To: Scott Garfinkle <seg at us.ibm.com>, libvir-list at redhat.com
> Date: 07/10/2017 06:41 AM
> Subject: Re: [libvirt] [PATCH] Use unsigned timeout in 
> cmdMigrateSetMaxDowntime
> 
> 
> 
> On 06/27/2017 11:19 AM, Scott Garfinkle wrote:
> > While looking to implement a migrate-getmaxdowntime command (coming),
> > I noticed that the setmaxdowntime is incorrectly looking at its
> > parameter as a signed longlong. Not sure how that got past gcc, but
> > here's a simple patch to make the command line parsing and the 
parameter to
> > the worker functions all have the correct (unsigned) type.
> > 
> > Signed-off-by: Scott Garfinkle <seg at us.ibm.com>
> > ---
> >  tools/virsh-domain.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> 
> "For some commands" allowing a -1 provides a mechanism to set an almost
> infinite time without having to type such a large value.  Still in this
> case since, the "downtime < 1" check immediately follows it seems that
> wouldn't be the case here!
Yes, and maybe removing that check would have been a better alternative? 
Still, thanks.
 
> Looking at QEMU code briefly - I do note the QEMU set downtime (and
> speed) commands that end up getting called are listed as "deprecated" in
> favor of migrate-set-parameters (downtime-limit and max-bandwidth, since
> QEMU 2.8).  So while you're at thinking about a getmaxdowntime type
> functionality maybe you'd want to give that a go as well (of course
> you'd have to add capabilities to detect when it was implemented using
> set-parameters)...

Thanks for pointing that out. So, I have patches to implement the 
get-maxdowntime, which would seem to be a separate but related effort. 
Being a newcomer to the code, I'll what are probably obvious questions: is 
the concern that qemu will eventually just stop providing that interface? 
Or, is there something inherently useful about changing the set-* 
commands? Otherwise, I'm not sure what the value to the code is of 
changing the already-working set commands.

regards, Scott Garfinkle

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