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

[Daniel P. Berrange]

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.

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

Daniel
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