Re: [Qemu-devel] [6388] Stop VM on ENOSPC error.

[Anthony Liguori]

Daniel P. Berrange wrote:
> On Wed, Feb 25, 2009 at 10:55:25AM -0600, Anthony Liguori wrote:
>   
> > Anthony Liguori wrote:
> >     
> > > Revision: 6388
> > >          http://svn.sv.gnu.org/viewvc/?view=rev&root=qemu&revision=6388
> > > Author:   aliguori
> > > Date:     2009-01-21 18:59:04 +0000 (Wed, 21 Jan 2009)
> > >
> > > Log Message:
> > > -----------
> > > Stop VM on ENOSPC error. (Gleb Natapov)
> > >
> > > This version of the patch adds new option "werror" to -drive flag.
> > > Possible values are:
> > >
> > > report    - report errors to a guest as IO errors
> > > ignore    - continue as if nothing happened
> > > stop      - stop VM on any error and retry last command on resume
> > > enospc    - stop vm on ENOSPC error and retry last command on resume
> > >            all other errors are reported to a guest.
> > >
> > > Default is "report" to maintain current behaviour.
> > >  
> > >       
> > I recently got burnt by the default being "report".  I was doing an 
> > installation and ran out of disk space.  The guest did not do anything 
> > intelligible with the error reports and froze very hard (as you'd expect).
> >
> > Any objection to changing to default to enospc?
> >     
>
> From a managment POV having QEMU change its state from running to
> paused behind our back is hard. You don't want to have to poll on
> 'info state' to see if the VM has paused, and QEMU provides us no
> async notification for this yet. So at this time, if QEMU auto-pauses
> we can't notice this change, and so again it'll just appear to the
> user as if it froze.
>   

I appreciate the difficulty but I don't think report is very much better 
from your perspective if it results in the guest completely freezing.

Regards,

Anthony Liguori

> If we get async notifications available via the monitor, then making 
> the default enospc is very sensible.
>
> Daniel
>