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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 18:14:44 -0000 (UTC)
> From: mlelstv%serpens.de@localhost (Michael van Elst)
> Message-ID: <s4veak$cl1$1%serpens.de@localhost>
> | + spb = vnd->sc_geom.vng_secsize / DEV_BSIZE;
>Do we know for sure here that vng_secsize >= DEV_BSIZE ?
>When I first used unix (long long ago) the drives I used had a
>sector size of 256 bytes (not DEC hardware.) (Floppies were
>128 bytes if I recall correctly).
>It would not be good if spb became 0 there.
I have also seen winchester disks with 128 byte sectors, ESDI
disks with 576 byte sectors and CD-ROM XA media uses 2352 byte
vng_secsize is either initialized to DEV_BSIZE or the value
is validated with DK_DEV_BSIZE_OK():
#define DK_DEV_BSIZE_OK(b) \
((b) >= DEV_BSIZE && ((b) & ((b) - 1)) == 0 && (b) <= MAXPHYS)
So dividing by DEV_BSIZE is ok.
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