[Qemu-devel] Re: [PATCH] vdi: Fix image opening and creation for odd disk sizes

[François Revol]

Le Fri, 07 May 2010 09:55:23 +0200, Kevin Wolf a écrit :
> Am 06.05.2010 20:29, schrieb Stefan Weil:
> > This patch fixes a regression introduced by commit
> > 95a2f9bc588c3f83375d87b0a9394f89a1bcfada.
> >
> > The fix is based on a patch from Kevin Wolf. Here his comment:
> >
> > "The number of blocks needs to be rounded up to cover all of the
> > virtual hard
> > disk. Without this fix, we can't even open our own images if their
> > size is not
> > a multiple of the block size."
> >
> > While Kevin's patch addressed vdi_create, my modification also
> > fixes
> > vdi_open which now accepts any image which is large enough to hold
> > the blocks.
>
> Shouldn't it be the other way round? That is, an image which has some
> unused blocks at its end makes sense, whereas an image with a virtual
> disk size that can't be represented with the number of blocks
> doesn't?

Exactly, else you don't create what you are asked for.

> > I also decided to keep the original code in vdi_create which rounds
> > down.
> > Rounding works in both directions, and there are good arguments for
> > both,
> > so I just left the original simple code.
> >
> > It is very important to use the rounded value for the new disk
> > size, too -
> > otherwise VirtualBox cannot open our disk image.
>
> So you're saying that in VDI you can't represent disks with an odd
> size?
> The one thing common across image formats seems to be that they are
> broken...

VB works quite well with my converted laptop image which indeed doesn't
end on block boundary.

Was it because you were just setting size larger than the covered by
the blocks ?

François.