Re: [Qemu-devel] [Qemu-trivial] [PATCH] vmdk: Fix cylinders number during convert

[Stefan Hajnoczi]

On Thu, Oct 23, 2014 at 10:03:25AM +0200, Markus Armbruster wrote:
> Michael Tokarev <address@hidden> writes:
> 
> > On 10/22/2014 05:25 PM, Arthur Gautier wrote:
> >> We can not rely on int cast to get a correct number of cylinders. The
> >> cylinders information was wrong in 49.9999% of cases.
> >> 
> >> This ensures the cylinders always gets the ceiling value.
> >
> > Good thing, especially the good probability :), and also a good patch
> > which comes with a test.
> >
> > But I wonder if anything can break this way?  Migration, windows guest
> > being unable to find its partitions, something else?
> >
> > And more.  What-if our drive size in cylinders will be larger than
> > the size in bytes?  The proposed div_round_up() will increase number
> > of cylinders, so size in CHS will be larger than size in bytes.  Maybe
> > there was a reason why originally the size in cylinders was calculated
> > by truncating extra fractional part?  What-if guest will try to access
> > the very last CHS which is incomplete?
> 
> Too many questions for -trivial, copying VMDK maintainers.

Fam: What do you think about this change?

Stefan

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