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

[Paolo Bonzini <pbonzini@redhat.com>]

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