tech-kern archive

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Old Index]

Re: I think I've found why Xen domUs can't mount some file-backed disk images! (vnd(4) hides labels!)



At Sun, 11 Apr 2021 16:06:27 -0000 (UTC), mlelstv%serpens.de@localhost (Michael van Elst) wrote:
Subject: Re: I think I've found why Xen domUs can't mount some file-backed disk images! (vnd(4) hides labels!)
>
> kre%munnari.OZ.AU@localhost (Robert Elz) writes:
>
> >    Date:        Sun, 11 Apr 2021 14:25:40 -0000 (UTC)
> >    From:        mlelstv%serpens.de@localhost (Michael van Elst)
> >    Message-ID:  <s4v0t4$5c8$1%serpens.de@localhost>
>
> >  | +       dg->dg_secperunit = vnd->sc_size / DEV_BSIZE;
>
> >While it shouldn't make any difference for any properly created image
> >file, make it be
>
> >			(vnd->sc_size + DEV_BSIZE - 1) / DEV_BSIZE;
>
> >so that any trailing partial sector remains in the image.
>
>
> The trailing partial sector is already ignored. Fortunately no disk image
> can even have a partial trailing sector and some magically implicit
> padding would have unexpected side effects.
>
> But the code also needs to be adjusted for different sector sizes.

So since vnd->sc_size is in units of disk blocks....

	dg->dg_secperunit =
	    ((vnd->sc_size * DEV_BSIZE) + DEV_BSIZE - 1) /
	    vnd->sc_geom.vng_secsize;

right?

--
					Greg A. Woods <gwoods%acm.org@localhost>

Kelowna, BC     +1 250 762-7675           RoboHack <woods%robohack.ca@localhost>
Planix, Inc. <woods%planix.com@localhost>     Avoncote Farms <woods%avoncote.ca@localhost>

Attachment: pgpK0N1GcAnOM.pgp
Description: OpenPGP Digital Signature



Home | Main Index | Thread Index | Old Index