On Tue, Apr 29, 2014 at 06:35:40PM +0200, J. Hannken-Illjes wrote:
> On 29 Apr 2014, at 18:23, Patrick Welche <pr...@cam.ac.uk> wrote:
>
> > On Tue, Apr 29, 2014 at 04:44:52PM +0100, Patrick Welche wrote:
> >> On Tue, Apr 29, 2014 at 04:08:02PM +0200, J. Hannken-Illjes wrote:
> >>> On 29 Apr 2014, at 15:19, Patrick Welche <pr...@cam.ac.uk> wrote:
> >>>
> >>> <snip>
> >>>>
> >>>> One oddity while perusing the code is:
> >>>>
> >>>> /*
> >>>> * Use pseudo-geometry specified. If none was provided,
> >>>> * use "standard" Adaptec fictitious geometry.
> >>>> */
> >>>> if (vio->vnd_flags & VNDIOF_HASGEOM) {
> >>>>
> >>>> memcpy(&vnd->sc_geom, &vio->vnd_geom,
> >>>> sizeof(vio->vnd_geom));
> >>>>
> >>>> How can VNDIOF_HASGEOM ever be set?
> >>>
> >>> With <geomspec> from vnconfig(8)?
> >>
> >> Ah thanks - I just used fxr.watson.org...
> >>
> >> It seems that disklabel and plist agree at least for sizes which are
> >> whole numbers of megabytes, e.g.,
> >>
> >> bytes:
> >> disklabel plist backing_file
> >> 10485760 10485760 10485760 = A00000
> >> 136314880 136314880 136314880 = 8200000
> >> 12761600 12582912 12761760 (this row in hex below)
> >> C2BA00 C00000 C2BAA0
> >
> > plist gets its idea of size by multiplying nsectors*ntracks*ncylinders.
> > disklabel gets its idea of size by rounding down the backing file size
> > to the nearest number of disk blocks.
> >
> > I am tempted to set plist's idea to sc_size as per the disklabel.
> > If I were to do that, I suspect I would break HASGEOM?
> >
> > OK to change struct vndgeom to add a vng_size member and set it as
> > appropriate according to HASGEOM? But then VNDIOC{SET,CLR}50 would
> > break?
> >
> > Thoughts?
>
> In vnd_set_geometry():
>
> - dg->dg_secperunit = (int64_t)vnd->sc_geom.vng_nsectors *
> - vnd->sc_geom.vng_ntracks * vnd->sc_geom.vng_ncylinders;
>
> + dg->dg_secperunit = vnd->sc_size;
>
> (completely untested of course ..)
That's what I meant by
"I am tempted to set plist's idea to sc_size"
But then "If I were to do that, I suspect I would break HASGEOM?"
?
Cheers,
Patrick
