[Qemu-devel] Re: [RFC 0/2]: QMP DISK_ERROR event

[Luiz Capitulino <lcapitulino@redhat.com>]

On Tue, 02 Feb 2010 10:25:19 +0100
Kevin Wolf <kwolf@redhat.com> wrote:

> Hi Luiz,
> 
> Am 01.02.2010 19:07, schrieb Luiz Capitulino:
> >  Hi there,
> > 
> >  I've been requested by libvirt guys to add a QMP event for disk I/O errors,
> > this is what this series is about.
> > 
> >  It's a RFC because I need feedback on the following:
> > 
> > 1. drive_get_on_error() is called on all disk errors, right?
> 
> Well, yes, it is for all devices that support rerror/werror. But it also
> might be called in other situations. Look at the "get" in the function
> name, it's really a getter function and not a event handler.
> 
> > 2. I've tested only ENOSPC errors, is there a way to test other errors? Like
> > read ones?
> 
> So you'll probably want some EIO. Some recent bugs I've been handling
> were a about images on NFS when the NFS server want away. It's a
> reliable way to get EIO (mount with -osoft and small timeouts). I guess
> qemu-nbd and the nbd: protocol might work, too.
> 
> Or maybe copy the start of a qcow2 image to a too small device.

 Thanks!

> > 3. Is this the right approach at all? :)
> 
> Yes and no. As I said above, drive_get_on_error() is not the right place
> to do it. Unfortunately it looks like there isn't a single generic place
> where it can be done, but the call to the event handler must be added to
> every device.

 Can't it be added to subsystems? Like ide, virtio etc?

 Maybe in the same function that calls driver_get_on_error()?