[Xen-devel] Re: [PATCH] Introduce dom0-min-space configuration option

[Michal Novotny <minovotn@xxxxxxxxxx>]

On 07/26/2010 01:31 PM, Paolo Bonzini wrote:
> On 07/26/2010 01:21 PM, Michal Novotny wrote:
> > On 07/26/2010 01:18 PM, Paolo Bonzini wrote:
> > > On 07/26/2010 12:36 PM, Michal Novotny wrote:
> > > > On 07/26/2010 11:59 AM, Paolo Bonzini wrote:
> > > > > On 07/26/2010 08:55 AM, Michal Novotny wrote:
> > > > > > Or do you think that we should alter the message in gunzip 
> > > > > > function to
> > > > > > say that there's an error in data stream (premature end of data
> > > > > > stream)
> > > > > > and that user should check for enough space on dom0?
> > > > > No, the gunzip function (in libxc, if I understood the context) 
> > > > > should
> > > > > not even be called if pygrub could not write the file. Instead, it
> > > > > should print something like
> > > > >
> > > > > pygrub: No space left on device
> > > > >
> > > > > and exit. There's absolutely no error checking here:
> > > > >
> > > > > data = fs.open_file(chosencfg["kernel"]).read()
> > > > > (tfd, bootcfg["kernel"]) = tempfile.mkstemp(prefix="boot_kernel.",
> > > > > dir="/var/run/xend/boot")
> > > > > os.write(tfd, data)
> > > > > os.close(tfd)
> > > > >
> > > > > (and likewise for initrd) and that's the bug.
> > > > >
> > > > > Paolo
> > > > Paolo, that's correct but the issue here is that we don't know 
> > > > until we
> > > > extract it from image file.
> > > os.write would return -1 and set errno to ENOSPC (besides, any other
> > > errno should get the same treatment), no?
> > Maybe, I need to check the docs first but you're most likely right about
> > this. Nevertheless this is the pygrub code AFAIK so some patch for xend
> > would be necessary as well, otherwise libvirt-based tools would complain
> > with "Boot loader didn't return any data!" message.
> That's the least of the problems, if a sensible error message is 
> present too.  I agree with Ian, let's first fix the main cause.  Then 
> we can see what the fallout is.
> Paolo
Well, the root cause is insufficient disk space since without 
insufficient disk space issue we won't be running into those issues. In 
fact there are 2 points of view on this one:
 1) implement a check for enough disk space (this is what I did)
 2) implement the proper error message saying there is not enough space 
to extract it (ENOSPC) - this is what you and Ian suggest
I am not telling any of those options is bad, nevertheless it's based 
just on the point of view. So, is option 2 better  and worth 
implementing rather than limiting the domain run only to case with 
enough space on dom0?
Michal


--
Michal Novotny<minovotn@xxxxxxxxxx>, RHCE
Virtualization Team (xen userspace), Red Hat


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